The SasS -SasR two-component signal transduction system required for early Myxococcus xanthus multicellular *development

Initiation of Myxococcus xanthus multicellular development requires both nutrient limitation and high cell density. The extracellular signal, A signal, which consists of a set of amino acids at specific concentrations, serves as a cell density signal in M. xanthus early development. A reporter gene, designated 4521, that requires both starvation and A signal for developmental expression was used to identify mutations in the signal transduction pathways. A group of point mutations located in the chromosomal sasB locus that bypasses both requirements was previously isolated. One of these point mutations, sasB7, was mapped to the sasS gene, which is predicted to encode a transmembrane histidine protein kinase required for normal development. SasS is a positive regulator of 4521 and a candidate A signal sensor. This dissertation continues the characterization of the sasB locus, focusing on the sasR gene and the functional relationship of SasS and SasR. ^ The sasR gene is located 2.2-kb downstream of sasS. It is predicted to encode an NtrC-like response regulator, which belongs to the family of sigma54 transcriptional activators. SasR is a positive regulator of 4521 gene and is required for normal development. The sasR mutant displays phenotypes similar to that of sasS mutant. Both SasS and SasR are required for the A-signal-dependent 4521 expression. Genetic epistasis analysis indicates that SasR functions downstream of SasS. Biochemical studies show that SasS has autokinase activity, and phosphorylated SasS is able to transfer its phosphate to SasR. We propose that SasS and SasR form a two-component signal transduction system in the A signal transduction pathway. ^ To search for the genes regulated by SasS and SasR, expression patterns of a group of developmental genes were compared in wild-type and sasS null mutant backgrounds. SasS and SasR were found to positively regulate sasN and 4521. The sasN gene was previously identified as a negative regulator of 4521, located at about 170-bp downstream of sasR. It is required for normal fruiting body development. Based on the above data, a regulatory network consisting of sasS, sasR, sasN, and 4521 is hypothesized, and the interactions of the components in this network can now be further studied. ^

Adherence to HIV /AIDS therapies among low -literacy populations: The ALP project

Adherence to HIV/AIDS therapies has been an important health problem since the early 1980s when AZT was first prescribed as a therapy for HIV/AIDS. It became particularly important between 1995 and 1997 with the advent of protease inhibitors (Chesney, Ickovics, Hecht, Sikipa, & Rabkin J., 1999) and became even more significant as persons with HIV/AIDS began to develop resistance to medications. Low-literacy populations have poorer health (Brez & Taylor, 1997) and higher AIDS rates (Simon, Hu, Diaz, & Kerndt, 1995), than their higher literacy counterparts due to delayed treatment (Baker, Parker, Williams, Clark, & Nurss, 1997), shame of literacy skills (Parikh, 1996), and poor access to care (Williams, et al., 1995). Poorer health and higher AIDS rates can also be attributed to poor patient-provider relationships (Crespo-Fierro, 1997; Eldred, Wu, Chaisson, & Moore, 1998) to a poorer understanding of medical protocols (Murphy, 1997), and inadequate patient education (Ungvarski, 1997; Davis, Michielutte, Askov, Williams, & Weiss, 1998, Doak, Doak, & Root, 1996). ^ The ALP intervention was developed for HIV positive low-literacy populations of African American women in Houston, Texas. The intervention was based on a needs assessment, using the PRECEDE model, an innovative process referred to as Intervention Mapping, and validated using formative evaluation methods with 54 individuals. The needs assessment resulted in a list of behavioral, environmental, predisposing, enabling, and reinforcing determinants of adherence. The Intervention Mapping framework was used to refine these determinants and develop a list of objectives describing what must be learned or changed to for the target population to adhere to HIV/AIDS therapies. Methods and strategies, were developed using theoretical constructs from the Health Belief Model (Rosenstock, 1974) and Social Cognitive Theory (Bandura, 1986). These theories, empirical evidence, and information from the target population indicated that perceived susceptibility, perceived severity, outcome expectations, and self-efficacy were important and changeable determinants of adherence to HIV/AIDS therapies for this population. ^ These components were brought together in the form of a theory-based color cartoon book and 10-minute cassette tape. The book was developed for people with 2.9 years of U.S. education as measured with the Flesch-Kincaid Grade Level method and the script was recorded onto a cassette tape to make it suitable for populations with even lower-literacy skills. A formative evaluation was conducted to ensure that the content and structure were accurate, clear, realistic, readable, appropriate, and likely to be used as intended. ^

Cell survival in early embryogenesis requires proper dosage of GCN5 and p300

Histone acetylation is a central event in transcriptional activation. The importance of this modification in mammalian development is highlighted by knockout studies that revealed loss of the histone acetyltransferases GCN5, p300, or CBP results in embryonic lethality. Furthermore, early embryogenesis is sensitive to the dosage of p300 and CBP since double p300 +/−CBP+/− heterozygotes die in utero, although either single heterozygote survives. PCAF and GCN5 physically interact with p300 and CBP in vitro. To determine whether these two groups of HATs interact functionally in vivo, we created mice lacking one or more allele of p300, GCN5 or PCAF. As expected, we found that mice heterozygous for any one of these null alleles are viable. The majority of GCN5 p300 double heterozygotes also survive to adulthood with no apparent abnormalities. However, a portion of these mice die prior to birth. These embryos are developmentally stunted and exhibit increased apoptosis compared to wild type or single GCN5 or p300 heterozygous littermates at E8.5. Tissue specification is unaffected in these embryos but organ formation is compromised. In contrast, no abnormalities were observed in mice harboring mutations in both PCAF and p300 , emphasizing the specificity of HAT functions in mammalian development. ^ Since GCN5 null embryos die early in embryogenesis because of a marked increase in apoptosis, studies of its function and mechanism in late development and in tissue specific differentiation are precluded. Here, we also report the establishment of a GCN5 null embryonic stem cell line and a conditional floxGCN5 mouse line, which will serve as powerful genetic tools to examine in depth the function of GCN5 in mammalian development and in adult tissues. ^