STUDIES ON THE CLASS I GLYCOPROTEINS OF THE MURINE MAJOR HISTOCOMPATIBILITY COMPLEX (TRANSPLANTATION ANTIGEN, LYMPHOCYTE, CELL SURFACE MOLECULE)

A series of studies were undertaken to analyze and compare various aspects of murine class I glycoproteins. An initial area of investigation characterized the Qa-1 alloantigens using two-dimensional gel electrophoresis. Analysis of the products of the Qa-1('b), Qa-1('c) and Qa-1('d) alleles indicated that these were distinct molecules as determined by their lack of comigration upon comparative two-dimensional gel analysis. The importance of asparagine-linked glycosylation in the cell surface expression of class I molecules was also examined. These studies employed tunicamycin, an inhibitor of N-linked glycosylation. Tunicamycin treatment of activated T lymphocytes diminished the surface expression of Qa-1 to undetectable levels; the levels of other class I molecules exhibited little or no decrease. These results indicated that N-linked glycosylation has a differential importance in the cell surface expression of various class I molecules. The molecular weight diversity of class I molecules was also investigated. Molecular weight determination of both the fully glycosylated and unglycosylated forms of H-2 and Qa/Tla region encoded molecules established that there is a significant variation in the sizes of these forms of various class I molecules. The most significant difference ((TURN)9,000 daltons) exists between the unglycosylated forms of H-2K('b) and Qa-2, suggesting that the structural organization of these two molecules may be very different. A comparative two-dimensional gel analysis of various class I glycoproteins isolated from resting and activated T and B lymphocytes indicated that class I molecules expressed on activated T cells exhibited an isoelectrophoretic pattern that was distinct from the isoelectrophoretic pattern of class I molecules expessed on the other cell populations. This difference was attributed to a lower sialic acid content of the molecules expressed on activated T cells. Analysis of cell homogenates determined that activated T cells contained a higher level of endogenous neuraminidase activity than was detected in the other populations, suggesting that this may be the basis of the lower sialic acid content. The relationship of the Qa-4 and Qa-2 alloantigens was also examined. It was established that upon mitogen activation, the expression of Qa-4 was greatly decreased, whereas Qa-2 expression was not decreased. However, an anti-Qa-2 monoclonal antibody blocked the binding of an anti-Qa-4 monoclonal antibody to resting cells. These studies established that Qa-4 is a determinant restricted to resting cells, which is closely associated on the surface with the Qa-2 molecule. ^

Transcriptional regulation and functional analysis of the Wilms' tumor gene WT1

The Wilms' tumor gene, WT1, encodes a zinc finger transcription factor which functions as a tumor suppressor. Defects in the WT1 gene can result in the development of nephroblastoma. WT1 is expressed during development, primarily in the metanephric kidney, the mesothelial lining of the abdomen and thorax, and the developing gonads. WT1 expression is tightly regulated and is essential for renal development. The WT1 gene encodes a protein with a proline-rich N-terminus which functions as a transcriptional repressor and C-terminus contains 4 zinc fingers that mediate DNA binding. WT1 represses transcription from a number of growth factors and growth factor receptors. WT1 mRNA undergoes alternative splicing at two sites, resulting in 4 mRNA species and polypeptide products. Exon 5, encoding 17 amino acids is alternatively spliced, and is located between the transcriptional repression domain and the DNA binding domain. The second alternative splice is the terminal 9 nucleotides of zinc finger 3, encoding the tripeptide Lys-Thr-Ser (KTS). The presence or absence of KTS within the zinc fingers of WT1 alters DNA binding.^ I have investigated transcriptional regulation of WT1, characterizing two means of repressing WT1 transcription. I have cloned a transcriptional silencer of the WT1 promoter which is located in the third intron of the WT1 gene. The silencer is 460 bp in length and contains an Alu repeat. The silencer functions in cells of non-renal origin.^ I have found that WT1 protein can autoregulate the WT1 promoter. Using the autoregulation of the WT1 promoter as a functional assay, I have defined differential consensus DNA binding motifs of WT1 isoforms lacking and containing the KTS tripeptide insertion. With these refined consensus DNA binding motifs, I have identified two additional targets of WT1 transcriptional repression, the proto-oncogenes bcl-2 and c-myc.^ I have investigated the ability of the alternatively spliced exon 5 to influence cell growth. In cell proliferation assays, isoforms of WT1 lacking exon 5 repress cell growth. WT1 isoforms containing exon 5 fail to repress cell growth to the same extent, but alter the morphology of the cells. These experiments demonstrate that the alternative splice isoforms of WT1 have differential effects on the function of WT1. These findings suggest a role for the alternative splicing of WT1 in metanephric development. ^

Contribution of the genes of the renin-angiotensin system to interindividual differences in blood pressure levels in Caucasians from Rochester, Minnesota

The Renin-Angiotensin system (RAS) regulates blood pressure through its effects on vascular tone, renal hemodynamics, and renal sodium and fluid balance. The genes encoding the four major components of the RAS, angiotensinogen, renin, angiotensin I-converting enzyme (ACE), and angiotensin II receptor type 1 (AT1), have been investigated as candidate genes in the pathogenesis of essential hypertension. However, studies have primarily focused on small samples of diseased individuals, and, therefore, have provided little information about the determinants of interindividual variation in blood pressure (BP) in the general population.^ Using data from a large population-based sample from Rochester, MN, I have evaluated the contribution of variation in the region of the RAS genes to interindividual variation in systolic, diastolic, and mean arterial pressure in the population-at-large. Marker genotype data from four polymorphisms located within or very near these genes were first collected on 3,974 individuals from 583 randomly ascertained three-generation pedigrees. Haseman-Elston regression and variance component methods of linkage analysis were then carried out to estimate the proportion of interindividual variance in BP attributable to the effects of variation at these four measured loci.^ A significant effect of the ACE locus on interindividual variation in mean arterial pressure (MAP) was detected in a sample of siblings belonging to the youngest generation. After allowing for measured covariates, this effect accounted for 15-25% of the interindividual variance in MAP, and was even greater in a subset with a positive family history of hypertension. When gender-specific analyses were carried out, this effect was significant in males but not in females. Extended pedigree analyses also provided evidence for an effect of the ACE locus on interindividual variation in MAP, but no difference between males and females was observed. Circumstantial evidence suggests that the ACE gene itself may be responsible for the observed effects on BP, although the possibility that other genes in the region may be at play cannot be excluded.^ No definitive evidence for an effect of the renin, angiotensinogen, or AT1 loci on interindividual variation in BP was obtained in this study, suggesting that the impact of these genes on BP may not be great in the Caucasian population-at-large. However, this does not preclude a larger effect of these genes in some subsets of individuals, especially among those with clinically manifest hypertension or coronary heart disease, or in other populations. ^

AN INVESTIGATION OF THE IMPACT OF CHILDREN WITH BIRTH DEFECTS ON STRESS IN THEIR FAMILIES

A child with a birth defect places physical, financial and emotional stress upon the family. The purpose of this study was to assess the impact of a mildly handicapped child on the family's coping abilities.^ Two groups, 101 mothers of children with birth defects and 107 mothers of intact children, completed the Holroyd Questionnaire on Resources and Stress and the Luborsky Social Assets Scale. From these groups, 86 pairs were matched on four factors: the age (two to eight years) and sex of the study child and the mother's education and marital status.^ The children with birth defects had completed the diagnostic evaluation at the Meyer Center for Developmental Pediatrics, Texas Children's Hospital. Children with severe defects were excluded. The mean I.Q of the group was 88, s.d. 17; 17 children were mildly retarded and 35 had an I.Q. of 100 or above; areas of dysfunction included motor abnormalities, behavior disturbance, speech problems, and sensory impairments.^ The expected direction and statistically significant differences were obtained from the data for the matched pairs on the Q.R.S. scales. The mothers of children with a birth defect reported poor health, a negative attitude toward the child, being over-protective, financial problems and feeling a lack of social support and family integration. They perceived the child as socially obtrusive, limited as to occupational opportunities, and as having a difficult personality.^ The functioning levels of the handicapped children contributed to the respondent's problems. The child with behavior and speech problems but adequate intelligence was a situation which resulted in a poor health/mood of the mother. The mother's pessimism was related to the child's low intelligence.^ The social assets of the respondents with intact children were significantly higher than those of respondents of handicapped children. There was no relationship between the total social assets score and the scores on the Q.R.S. for mothers of handicapped children. These mothers did report poorer physical conditions, more smoking, and quarreling of their parents as they grew up. ^

The transcriptional regulation of the {\it neu\/} gene: Examples of activation, repression, and cell-specific expression

The neu oncogene encodes a growth factor receptor-like protein, p185, with an intrinsic tyrosine kinase activity. A single point mutation, an A to T transversion resulting in an amino acid substitution from valine to glutamic acid, in the transmembrane domain of the rat neu gene was found to be responsible for the transforming and tumorigenic phenotype of the cells that carry it. In contrast, the human proto-neu oncogene is frequently amplified in tumors and cell lines derived from tumors and the human neu gene overexpression/amplification in breast and ovarian cancers is known to correlate with poor patient prognosis. Examples of the human neu gene overexpression in the absence of gene amplification have been observed, which may suggest the significant role of the transcriptional and/or post-transcriptional control of the neu gene in the oncogenic process. However, little is known about the transcriptional mechanisms which regulate the neu gene expression. In this study, three examples are presented to demonstrate the positive and negative control of the neu gene expression.^ First, by using band shift assays and methylation interference analyses, I have identified a specific protein-binding sequence, AAGATAAAACC ($-$466 to $-$456), that binds a specific trans-acting factor termed RVF (for EcoRV factor on the neu promoter). The RVF-binding site is required for maximum transcriptional activity of the rat neu promoter. This same sequence is also found in the corresponding regions of both human and mouse neu promoters. Furthermore, this sequence can enhance the CAT activity driven by a minimum promoter of the thymidine kinase gene in an orientation-independent manner, and thus it behaves as an enhancer. In addition, Southwestern (DNA-protein) blot analysis using the RVF-binding site as a probe points to a 60-kDa polypeptide as a potential candidate for RVF.^ Second, it has been reported that the E3 region of adenovirus 5 induces down-regulation of epidermal growth factor (EGF) receptor through endocytosis. I found that the human neu gene product, p185, (an EGF receptor-related protein) is also down-regulated by adenovirus 5, but via a different mechanism. I demonstrate that the adenovirus E1a gene is responsible for the repression of the human neu gene at the transcriptional level.^ Third, a differential expression of the neu gene has been found in two cell model systems: between the mouse fibroblast Swiss-Webster 3T3 (SW3T3) and its variant NR-6 cells; and between the mouse liver tumor cell line, Hep1-a, and the mouse pancreas tumor cell line, 266-6. Both NR-6 and 266-6 cell lines are not able to express the neu gene product, p185. I demonstrate that, in both cases, the transcriptional repression of the neu gene may account for the lack of the p185 expression in these two cell lines. ^

Role of the N- and C-lobes of calmodulin in the activation of Ca(2+)/calmodulin-dependent protein kinase II.

Understanding the principles of calmodulin (CaM) activation of target enzymes will help delineate how this seemingly simple molecule can play such a complex role in transducing Ca (2+)-signals to a variety of downstream pathways. In the work reported here, we use biochemical and biophysical tools and a panel of CaM constructs to examine the lobe specific interactions between CaM and CaMKII necessary for the activation and autophosphorylation of the enzyme. Interestingly, the N-terminal lobe of CaM by itself was able to partially activate and allow autophosphorylation of CaMKII while the C-terminal lobe was inactive. When used together, CaMN and CaMC produced maximal CaMKII activation and autophosphorylation. Moreover, CaMNN and CaMCC (chimeras of the two N- or C-terminal lobes) both activated the kinase but with greater K act than for wtCaM. Isothermal titration calorimetry experiments showed the same rank order of affinities of wtCaM > CaMNN > CaMCC as those determined in the activity assay and that the CaM to CaMKII subunit binding ratio was 1:1. Together, our results lead to a proposed sequential mechanism to describe the activation pathway of CaMKII led by binding of the N-lobe followed by the C-lobe. This mechanism contrasts the typical sequential binding mode of CaM with other CaM-dependent enzymes, where the C-lobe of CaM binds first. The consequence of such lobe specific binding mechanisms is discussed in relation to the differential rates of Ca (2+)-binding to each lobe of CaM during intracellular Ca (2+) oscillations.

cAMP-dependent protein kinase and heterologous desensitization of the adenylyl cyclase

Previous experiments had shown no differences in desensitization in cells with mutations of the adenylyl cyclase or the cAMP-dependent protein kinase and had ruled out this kinase as a mediator of desensitization; however, the assays of adenylyl cyclase had been made at high concentrations of free magnesium. The work presented in this dissertation documents a role for cAMP-dependent protein kinase which became apparent with assays at low concentrations of free magnesium. (1) The adenylyl cyclase in membranes from wild type S49 lymphoma cells showed substantial desensitization after incubation of the intact cells with low concentrations of epinephrine (5-20 nM). This desensitization was heterologous, that is it reduced the subsequent responses of the adenylyl cyclase to both epinephrine and prostaglandin-E$\sb1$. (2) The adenylyl cyclase in membranes of S49 cyc$\sp-$ cells, which do not make cAMP in response to hormones, and S49 kin$\sp-$ cells, which lack cAMP-dependent protein kinase activity, showed no heterologous desensitization following incubation of the intact cells with low concentrations of hormones. (3) Heterologous desensitization of the adenylyl cyclase was induced by incubations of wild type cells with forskolin, which activates the adenylyl cyclase downstream of the hormone receptors, or dibutyryl-cAMP, which activates the cAMP-dependent protein kinase directly. (4) Site-directed mutagenesis was used to delete the cAMP-dependent protein kinase consensus phosphorylation sequences on the $\beta$-adrenergic receptor. Heterologous desensitization occurred in intact L-cells expressing the wild type receptor or the receptor lacking the C-terminal phosphorylation site; however, only homologous desensitization occurred when the phosphorylation site on the third intracellular loop of the receptor was deleted. (5) To test directly the effects of cAMP-dependent protein kinase on the adenylyl cyclase the catalytic subunit of the kinase was purified from bovine heart and incubated with adenylyl cyclase in plasma membrane preparations. In this cell-free system the kinase caused rapid heterlogous reductions of the responsiveness of the S49 wild type adenylyl cyclase. Additionally, the adenylyl cyclase in kin$\sp-$ membranes, which showed only homologous desensitization in the intact cell, was desensitization by cell-free incubation with the kinase.^ The epinephrine responsiveness was not affected in L-cell membranes expressing the $\beta$-adrenergic receptor lacking the cAMP-dependent protein kinase consensus sequence on the third intracellular loop. ^

Cloning and characterization of the full length cDNA and promoter of mouse tissue transglutaminase

Transglutaminases are a family of enzymes that catalyze the covalent cross-linking of proteins through the formation of $\varepsilon$-($\gamma$-glutaminyl)-lysyl isopeptide bonds. Tissue transglutaminase (Tgase) is an intracellular enzyme which is expressed in terminally differentiated and senescent cells and also in cells undergoing apoptotic cell death. To characterize this enzyme and examine its relationship with other members of the transglutaminase family, cDNAs, the first two exons of the gene and 2 kb of the 5$\sp\prime$ flanking region, including the promoter, were isolated. The full length Tgase transcript consists of 66 bp of 5$\sp\prime$-UTR (untranslated) sequence, an open reading frame which encodes 686 amino acids and 1400 bp of 3$\sp\prime$-UTR sequence. Alignment of the deduced Tgase protein sequence with that of other transglutaminases revealed regions of strong homology, particularly in the active site region.^ The Tgase cDNA was used to isolate and characterize a genomic clone encompassing the 5$\sp\prime$ end of the mouse Tgase gene. The transcription start site was defined using genomic and cDNA clones coupled with S1 protection analysis and anchored PCR. This clone includes 2.3 kb upstream of the transcription start site and two exons that contain the first 256 nucleotides of the mouse Tgase cDNA sequence. The exon intron boundaries have been mapped and compared with the exon intron boundaries of three members of the transglutaminase family: human factor XIIIa, the human keratinocyte transglutaminase and human erythrocyte band 4.1. Tissue Tgase exon II is similar to comparable exons of these genes. However, exon I bears no resemblance with any of the other transglutaminase amino terminus exons.^ Previous work in our laboratory has shown that the transcription of the Tgase gene is directly controlled by retinoic acid and retinoic acid receptors. To identify the region of the Tgase gene responsible for regulating its expression, fragments of the Tgase promoter and 5$\sp\prime$-flanking region were cloned into the chloramphenicol actetyl transferase (CAT) reporter constructs. Transient transfection experiments with these constructs demonstrated that the upstream region of Tgase is a functional promoter which contains a retinoid response element within a 1573 nucleotide region spanning nucleotides $-$252 to $-$1825. ^

Characterization of the cholesterol 7$\alpha$-hydroxylase promoter in hypercholesterolemia -resistant rabbits

Our laboratory has developed and partially characterized a strain of New Zealand white rabbits that are resistant to the hypercholesterolemia which typically occurs in normal rabbits when fed a cholesterol-enriched diet. This phenotype is most likely attributed to an increase in bile acid excretion by hypercholesterolemia-resistant (CRT) rabbits as a result of elevated enzyme activity of cholesterol 7$\alpha$-hydroxylase (C7$\alpha$H), the rate-limiting enzyme in bile acid synthesis. Northern analysis revealed that CRT rabbits, in comparison to normal rabbits, have a 7-fold greater steady-state C7$\alpha$H mRNA levels irrespective of dietary regimen. The C7$\alpha$H gene in both phenotypes was determined to be a single copy gene. The hypothesis was that the elevated C7$\alpha$H mRNA levels in CRT rabbits, in comparison to normal animals, was due to an increase in the transcription rate of the C7$\alpha$H gene as a result of a mutation in a cis-acting element and/or a trans-acting factor within the hepatocyte. To isolate the C7$\alpha$H gene from both normal and CRT rabbits, genomic libraries were prepared from both phenotypes into $\lambda$GEM12 vectors using conventional techniques. Three CRT and one normal phage clones that contained the C7$\alpha$H gene were identified by screening the library with a series of probes located within different exons of the C7$\alpha$H cDNA. Sequencing analysis confirmed that approximately 1100 bp of the C7$\alpha$H 5'-flanking region from both normal and CRT phenotypes was identical. The increase in C7$\alpha$H mRNA levels was not attributed to a cis-acting mutation within this region. Liver nuclear extracts were prepared from normal and CRT rabbits maintained either on a basal or 0.25% cholesterol-enriched diet and incubated with several radiolabeled DNA fragments from the C7$\alpha$H gene. A 37 basepair region, located between nucleotides $-$452 to $-$416 was identified that had altered binding patterns between normal and CRT rabbits as a function of diet. Two additional regions, $-$747 to $-$575 and $-$580 to $-$442, produced banding patterns which were identical, irrespective of phenotype or diet. In conclusion, these studies suggested that the increase in C7$\alpha$H mRNA in CRT rabbits was due to differences in binding of a cholesterol-responsive transcription factor to the C7$\alpha$H promoter. ^

The functional role of the tumor suppressor MMAC /PTEN in glioblastoma multiforme and prostate cancer

Investigations into the molecular basis of glioblastoma multiforme led to the identification of a putative tumor suppressor gene, MMAC/ PTEN. Initial studies implicated MMAC/PTEN in many different tumor types, and identified a protein phosphatase motif in its sequence. This project aimed to identify the biological and biochemical functions of MMAC/PTEN by transiently expressing the gene in cancer cells that lack a functional gene product. ^ Expression of MMAC/PTEN mildly suppressed the growth of U251 human glioma cells and abrogated the growth advantage mediated by overexpression of the epidermal growth factor receptor (EGFR). Immunoblotting demonstrated that MMAC/PTEN expression did not affect the phosphorylation of the EGFR itself, or the intermediates of several downstream signaling pathways. However, MMAC/PTEN expression significantly reduced the phosphorylation and catalytic activity of the proto-oncogene Akt/PKB. While Akt/PKB regulates the survival of many cell types, expression of MMAC/PTEN did not induce apoptosis in adherent U251 cells. Instead, MMAC/PTEN expression sensitized the cells to apoptosis when maintained in suspension (anoikis). As the survival of suspended cells is one of the hallmarks leading to metastasis, MMAC/PTEN expression was examined in a system in which metastasis is more clinically relevant, prostate cancer. ^ Expression of MMAC/PTEN in both LNCaP and PC3-P human prostate cancer cells specifically inhibited Akt/PKB phosphorylation. MMAC/PTEN expression in LNCaP cells resulted in a profound inhibition of growth that was significantly greater than that achieved with expression of p53. Expression of MMAC/PTEN in PC3-P cells resulted in greater growth inhibition than was observed in U251 glioma cells, but less than was observed in LNCaP cells, or upon p53 expression. To determine if MMAC/PTEN could function as a tumor suppressor in vivo, the effects of MMAC/PTEN expression on PC3-P cells implanted orthotopically in nude mice were examined. The ex-vivo expression of MMAC/PTEN did not decrease tumor incidence, but it did significantly decrease tumor size and metastasis. In-vivo expression of MMAC/PTEN in pre-established PC3-P tumors did not significantly inhibit tumor incidence or size, but did inhibit metastasis formation. ^ These studies demonstrate that MMAC/PTEN is a novel and important tumor suppressor gene, which functions to downregulate an important cell survival signaling pathway. ^

The role of Ski/Sno oncoproteins as negative regulators of the TGF-beta/SMAD signaling pathway in B -cell non -Hodgkin's lymphoma (NHL-B)

Non-Hodgkin's lymphomas are common tumors of the human immune system, primarily of B cell lineage (NHL-B). Negative growth regulation in the B cell lineage is mediated primarily through the TGF-β/SMAD signaling pathway that regulates a variety of tumor suppressor genes. Ski was originally identified as a transforming oncoprotein, whereas SnoN is an isoform of the Sno protein that shares a large region of homology with Ski. In this study, we show that Ski/SnoN are endogenously over-expressed both in patients' lymphoma cells and NHL-B cell lines. Exogenous TGF-β1 treatment induces down-regulation of Ski and SnoN oncoprotein expression in an NHL-B cell line, implying that Ski and SnoN modulate the TGF-β signaling pathway and are involved in cell growth regulation. Furthermore, we have developed an NHL-B cell line (DB) that has a null mutation in TGF-β receptor type II. In this mutant cell line, Ski/SnoN proteins are not down-regulated in response to TGF-β1 treatment, suggesting that downregulation of Ski and SnoN proteins in NHL-B require an intact functional TGF-β signaling pathway Resting normal B cells do not express Ski until activated by antigens and exogenous cytokines, whereas a low level of SnoN is also present in peripheral blood Go B cells. In contrast, autonomously growing NHL-B cells over-express Ski and SnoN, implying that Ski and SnoN are important cell cycle regulators. To further investigate a possible link between reduction of the Ski protein level and growth inhibition, Ski antisense oligodeoxynucleotides were transfected into NHL-B cells. The Ski protein level was found to decrease to less than 40%, resulting in restoring the effect of TGF-β and leading to cell growth inhibition and G1 cell cycle arrest. Co-immunoprecipitation experiments demonstrated that Ski associates with Smad4 in the nucleus, strongly suggesting that over-expression of the nuclear protein Ski and/or SnoN negatively regulates the TGF-β pathway, possibly by modulating Smad-mediated tumor suppressor gene expression. Together, in NHL-B, the TGF-β/SMAD growth inhibitory pathway is usually intact, but over-expression of the Ski and/or SnoN, which binds to Smad4, abrogates the negative regulatory effects of TGF-β/SMAD in lymphoma cell growth and potentiates the growth potential of neoplastic B cells. ^

Determinants of cervical cancer screening among women workers in Monterrey, Mexico

Introduction. Cervical cancer is the most common and lethal cancer among Mexican women. A nationwide cervical cancer screening program established in 1974 has had little impact on cervical cancer incidence or mortality rates. This case-control study was designed to determine the association between knowledge factors and structural, organizational, and sociocultural perceptions related to adherence to cervical cancer screening guidelines among women living and working in Monterrey, Mexico.^ Methods. Cases were defined as sexually active female store clerks ages 18-64 who do not adhere to cervical cancer screening guidelines in accordance with the Official Mexican Standard (Norma Oficial Mexicana, NOM 014-SSA2-1994). Controls were defined as sexually active female store clerks ages 18-64 who do adhere to cervical cancer screening guidelines in accordance with the NOM. Participants (N = 229) answered survey questions regarding cervical cancer screening practices as well as their knowledge and perceptions about screening for cervical cancer. Two multivariate logistic regression models were built to analyze (1) knowledge factors and (2) perceptions significantly associated with adherence in univariate analysis.^ Results. Having no or inaccurate knowledge of national cervical cancer screening guidelines (OR = 11.05, 95%CI: 4.28, 28.54) and no knowledge of the utility of the Papanicolaou (Pap) exam (OR = 6.77, 95%CI: 0.99, 46.43) were risk factors for non-adherence to cervical cancer screening guidelines. Perceptions of fear or embarrassment of the Pap exam (OR = 16.17, 95%CI: 5.08, 51.49) and lower levels of spousal or partner acceptance of the Pap exam (OR = 5.82, 95%CI: 1.34, 25.31) were risk factors for non-adherence to cervical cancer screening guidelines.^ Conclusion. Knowledge factors and sociocultural perceptions related to cervical cancer screening were strong predictors of adherence to screening guidelines. Future studies may be able to further explore these findings with larger sample sizes and in other populations in Mexico. By identifying these factors, future population-specific recommendations and interventions to increase screening rates can be formulated with the long-term goal of reducing morbidity and mortality from cervical cancer among Mexican women.^