Spatio-temporal distribution of fatty acid-binding protein 6 (fabp6) gene transcripts in the developing and adult zebrafish (Danio rerio)

We have determined the structure of the fatty acid-binding protein 6 (fabp6) gene and the tissue-specific distribution of its transcripts in embryos, larvae and adult zebrafish (Danio rerio). Like most members of the vertebrate FABP multigene family, the zebrafish fabp6 gene contains four exons separated by three introns. The coding region of the gene and expressed sequence tags code for a polypeptide of 131 amino acids (14 kDa, pI 6.59). The putative zebrafish Fabp6 protein shared greatest sequence identity with human FABP6 (55.3%) compared to other orthologous mammalian FABPs and paralogous zebrafish Fabps. Phylogenetic analysis showed that the zebrafish Fabp6 formed a distinct clade with the mammalian FABP6s. The zebrafish fabp6 gene was assigned to linkage group (chromosome) 21 by radiation hybrid mapping. Conserved gene synteny was evident between the zebrafish fabp6 gene on chromosome 21 and the FABP6/Fabp6 genes on human chromosome 5, rat chromosome 10 and mouse chromosome 11. Zebrafish fabp6 transcripts were first detected in the distal region of the intestine of embryos at 72 h postfertilization. This spatial distribution remained constant to 7-day-old larvae, the last stage assayed during larval development. In adult zebrafish, fabp6 transcripts were detected by RT-PCR in RNA extracted from liver, heart, intestine, ovary and kidney (most likely adrenal tissue), but not in RNA from skin, brain, gill, eye or muscle. In situ hybridization of a fabp6 riboprobe to adult zebrafish sections revealed intense hybridization signals in the adrenal homolog of the kidney and the distal region of the intestine, and to a lesser extent in ovary and liver, a transcript distribution that is similar, but not identical, to that seen for the mammalian FABP6/Fabp6 gene. © 2008 The Authors.

Loss of nuclear poly(A)-binding protein 1 (PABPN1) causes defects in myogenesis and mRNA biogenesis

The nuclear poly(A)-binding protein 1 (PABPN1) is a ubiquitously expressed protein that plays a critical role in polyadenylation. Short expansions of the polyalanine tract in the N-terminus of PABPN1 lead to oculopharyngeal muscular dystrophy (OPMD), which is an adult onset disease characterized by eyelid drooping, difficulty in swallowing and weakness in the proximal limb muscles. Although significant data from in vitro biochemical assays define the function of PABPN1 in control of poly(A) tail length, little is known about the role of PABPN1 in mammalian cells. To assess the function of PABPN1 in mammalian cells and specifically in cells affected in OPMD, we examined the effects of PABPN1 depletion using siRNA in primary mouse myoblasts from extraocular, pharyngeal and limb muscles. PABPN1 knockdown significantly decreased cell proliferation and myoblast differentiation during myogenesis in vitro. At the molecular level, PABPN1 depletion in myoblasts led to a shortening of mRNA poly(A) tails, demonstrating the cellular function of PABPN1 in polyadenylation control in a mammalian cell. In addition, PABPN1 depletion caused nuclear accumulation of poly(A) RNA, revealing that PABPN1 is required for proper poly(A) RNA export from the nucleus. Together, these experiments demonstrate that PABPN1 plays an essential role in myoblast proliferation and differentiation, suggesting that it is required for muscle regeneration and maintenance in vivo.

Double-Stranded RNA-Activated Protein Kinase Is a Key Modulator of Insulin Sensitivity in Physiological Conditions and in Obesity in Mice

The molecular integration of nutrient-and pathogen-sensing pathways has become of great interest in understanding the mechanisms of insulin resistance in obesity. The double-stranded RNA-dependent protein kinase (PKR) is one candidate molecule that may provide cross talk between inflammatory and metabolic signaling. The present study was performed to determine, first, the role of PKR in modulating insulin action and glucose metabolism in physiological situations, and second, the role of PKR in insulin resistance in obese mice. We used Pkr(-/-) and Pkr(+/+) mice to investigate the role of PKR in modulating insulin sensitivity, glucose metabolism, and insulin signaling in liver, muscle, and adipose tissue in response to a high-fat diet. Our data show that in lean Pkr(-/-) mice, there is an improvement in insulin sensitivity, and in glucose tolerance, and a reduction in fasting blood glucose, probably related to a decrease in protein phosphatase 2A activity and a parallel increase in insulin-induced thymoma viral oncogene-1 (Akt) phosphorylation. PKR is activated in tissues of obese mice and can induce insulin resistance by directly binding to and inducing insulin receptor substrate (IRS)-1 serine307 phosphorylation or indirectly through modulation of c-Jun N-terminal kinase and inhibitor of kappa B kinase beta. Pkr(-/-) mice were protected from high-fat diet-induced insulin resistance and glucose intolerance and showed improved insulin signaling associated with a reduction in c-Jun N-terminal kinase and inhibitor of kappa B kinase beta phosphorylation in insulin-sensitive tissues. PKR may have a role in insulin sensitivity under normal physiological conditions, probably by modulating protein phosphatase 2A activity and serine-threonine kinase phosphorylation, and certainly, this kinase may represent a central mechanism for the integration of pathogen response and innate immunity with insulin action and metabolic pathways that are critical in obesity. (Endocrinology 153:5261-5274, 2012)

Retinol binding protein 4 and retinol in steatotic and nonsteatotic rat livers in the setting of partial hepatectomy under ischemia/reperfusion

Steatotic livers show increased hepatic damage and impaired regeneration after partial hepatectomy (PH) under ischemia/reperfusion (I/R), which is commonly applied in clinical practice to reduce bleeding. The known function of retinol-binding protein 4 (RBP4) is to transport retinol in the circulation. We examined whether modulating RBP4 and/or retinol could protect steatotic and nonsteatotic livers in the setting of PH under I/R. Steatotic and nonsteatotic livers from Zucker rats were subjected to PH (70%) with 60 minutes of ischemia. RBP4 and retinol levels were measured and altered pharmacologically, and their effects on hepatic damage and regeneration were studied after reperfusion. Decreased RBP4 levels were observed in both liver types, whereas retinol levels were reduced only in steatotic livers. RBP4 administration exacerbated the negative consequences of liver surgery with respect to damage and liver regeneration in both liver types. RBP4 affected the mobilization of retinol from steatotic livers, and this revealed actions of RBP4 independent of simple retinol transport. The injurious effects of RBP4 were not due to changes in retinol levels. Treatment with retinol was effective only for steatotic livers. Indeed, retinol increased hepatic injury and impaired liver regeneration in nonsteatotic livers. In steatotic livers, retinol reduced damage and improved regeneration after surgery. These benefits of retinol were associated with a reduced accumulation of hepatocellular fat. Thus, strategies based on modulating RBP4 could be ineffective and possibly even harmful in both liver types in the setting of PH under I/R. In terms of clinical applications, a retinol pretreatment might open new avenues for liver surgery that specifically benefit the steatotic liver. Liver Transpl 18:1198-1208, 2012. (c) 2012 AASLD.

Alba-domain proteins of Trypanosoma brucei are cytoplasmic RNA-binding proteins that interact with the translation machinery

Trypanosoma brucei and related pathogens transcribe most genes as polycistronic arrays that are subsequently processed into monocistronic mRNAs. Expression is frequently regulated post-transcriptionally by cis-acting elements in the untranslated regions (UTRs). GPEET and EP procyclins are the major surface proteins of procyclic (insect midgut) forms of T. brucei. Three regulatory elements common to the 3' UTRs of both mRNAs regulate mRNA turnover and translation. The glycerol-responsive element (GRE) is unique to the GPEET 3' UTR and regulates its expression independently from EP. A synthetic RNA encompassing the GRE showed robust sequence-specific interactions with cytoplasmic proteins in electromobility shift assays. This, combined with column chromatography, led to the identification of 3 Alba-domain proteins. RNAi against Alba3 caused a growth phenotype and reduced the levels of Alba1 and Alba2 proteins, indicative of interactions between family members. Tandem-affinity purification and co-immunoprecipitation verified these interactions and also identified Alba4 in sub-stoichiometric amounts. Alba proteins are cytoplasmic and are recruited to starvation granules together with poly(A) RNA. Concomitant depletion of all four Alba proteins by RNAi specifically reduced translation of a reporter transcript flanked by the GPEET 3' UTR. Pulldown of tagged Alba proteins confirmed interactions with poly(A) binding proteins, ribosomal protein P0 and, in the case of Alba3, the cap-binding protein eIF4E4. In addition, Alba2 and Alba3 partially cosediment with polyribosomes in sucrose gradients. Alba-domain proteins seem to have exhibited great functional plasticity in the course of evolution. First identified as DNA-binding proteins in Archaea, then in association with nuclear RNase MRP/P in yeast and mammalian cells, they were recently described as components of a translationally silent complex containing stage-regulated mRNAs in Plasmodium. Our results are also consistent with stage-specific regulation of translation in trypanosomes, but most likely in the context of initiation.

Posttranslational modification of the AU-rich element binding protein HuR by protein kinase Cdelta elicits angiotensin II-induced stabilization and nuclear export of cyclooxygenase 2 mRNA

The mRNA stabilizing factor HuR is involved in the posttranscriptional regulation of many genes, including that coding for cyclooxygenase 2 (COX-2). Employing RNA interference technology and actinomycin D experiments, we demonstrate that in human mesangial cells (hMC) the amplification of cytokine-induced COX-2 by angiotensin II (AngII) occurs via a HuR-mediated increase of mRNA stability. Using COX-2 promoter constructs with different portions of the 3' untranslated region of COX-2, we found that the increase in COX-2 mRNA stability is attributable to a distal class III type of AU-rich element (ARE). Likewise, the RNA immunoprecipitation assay showed AngII-induced binding of HuR to this ARE. Using the RNA pulldown assay, we demonstrate that the AngII-caused HuR assembly with COX-2 mRNA is found in free and cytoskeleton-bound polysomes indicative of an active RNP complex. Mechanistically, the increased HuR binding to COX-2-ARE by AngII is accompanied by increased nucleocytoplasmic HuR shuttling and depends on protein kinase Cdelta (PKCdelta), which physically interacts with nuclear HuR, thereby promoting its phosphorylation. Mapping of phosphorylation sites identified serines 221 and 318 as critical target sites for PKCdelta-triggered HuR phosphorylation and AngII-induced HuR export to the cytoplasm. Posttranslational modification of HuR by PKCdelta represents an important novel mode of HuR activation implied in renal COX-2 regulation.

Tumor necrosis factor-alpha upregulates 11beta-hydroxysteroid dehydrogenase type 1 expression by CCAAT/enhancer binding protein-beta in HepG2 cells

The enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) catalyzes the conversion of inactive to active glucocorticoids. 11beta-HSD1 plays a crucial role in the pathogenesis of obesity and controls glucocorticoid actions in inflammation. Several studies have demonstrated that TNF-alpha increases 11beta-HSD1 mRNA and activity in various cell models. Here, we demonstrate that mRNA and activity of 11beta-HSD1 is increased in liver tissue from transgenic mice overexpressing TNF-alpha, indicating that this effect also occurs in vivo. To dissect the molecular mechanism of this increase, we investigated basal and TNF-alpha-induced transcription of the 11beta-HSD1 gene (HSD11B1) in HepG2 cells. We found that TNF-alpha acts via p38 MAPK pathway. Transient transfections with variable lengths of human HSD11B1 promoter revealed highest activity with or without TNF-alpha in the proximal promoter region (-180 to +74). Cotransfection with human CCAAT/enhancer binding protein-alpha (C/EBPalpha) and C/EBPbeta-LAP expression vectors activated the HSD11B1 promoter with the strongest effect within the same region. Gel shift and RNA interference assays revealed the involvement of mainly C/EBPalpha, but also C/EBPbeta, in basal and only of C/EBPbeta in the TNF-alpha-induced HSD11B1 expression. Chromatin immunoprecipitation assay confirmed in vivo the increased abundance of C/EBPbeta on the proximal HSD11B1 promoter upon TNF-alpha treatment. In conclusion, C/EBPalpha and C/EBPbeta control basal transcription, and TNF-alpha upregulates 11beta-HSD1, most likely by p38 MAPK-mediated increased binding of C/EBPbeta to the human HSD11B1 promoter. To our knowledge, this is the first study showing involvement of p38 MAPK in the TNF-alpha-mediated 11beta-HSD1 regulation, and that TNF-alpha stimulates enzyme activity in vivo.

The stem-loop binding protein stimulates histone translation at an early step in the initiation pathway

Metazoan replication-dependent histone mRNAs do not have a poly(A) tail but end instead in a conserved stem-loop structure. Efficient translation of these mRNAs is dependent on the stem-loop binding protein (SLBP). Here we explore the mechanism by which SLBP stimulates translation in vertebrate cells, using the tethered function assay and analyzing protein-protein interactions. We show for the first time that translational stimulation by SLBP increases during oocyte maturation and that SLBP stimulates translation at the level of initiation. We demonstrate that SLBP can interact directly with subunit h of eIF3 and with Paip1; however, neither of these interactions is sufficient to mediate its effects on translation. We find that Xenopus SLBP1 functions primarily at an early stage in the cap-dependent initiation pathway, targeting small ribosomal subunit recruitment. Analysis of IRES-driven translation in Xenopus oocytes suggests that SLBP activity requires eIF4E. We propose a model in which a novel factor contacts eIF4E bound to the 5' cap and SLBP bound to the 3' end simultaneously, mediating formation of an alternative end-to-end complex.

Sp1 up-regulates cAMP-response-element-binding protein expression during retinoic acid-induced mucous differentiation of normal human bronchial epithelial cells.

CREB [CRE (cAMP-response element)-binding protein] is an important transcription factor that is differentially regulated in cells of various types. We recently reported that RA (retinoic acid) rapidly activates CREB without using RARs (RA receptors) or RXRs (retinoid X receptors) in NHTBE cells (normal human tracheobronchial epithelial cells). However, little is known about the role of RA in the physiological regulation of CREB expression in the early mucous differentiation of NHTBE cells. In the present study, we report that RA up-regulates CREB gene expression and that, using 5'-serial deletion promoter analysis and mutagenesis analyses, two Sp1 (specificity protein 1)-binding sites located at nt -217 and -150, which flank the transcription initiation site, are essential for RA induction of CREB gene transcription. Furthermore, we found that CREs located at nt -119 and -98 contributed to basal promoter activity. Interestingly, RA also up-regulated Sp1 in a time- and dose-dependent manner. Knockdown of endogenous Sp1 using siRNA (small interfering RNA) decreased RA-induced CREB gene expression. However, the converse was not true: knockdown of CREB using CREB siRNA did not affect RA-induced Sp1 gene expression. We conclude that RA up-regulates CREB gene expression during the early stage of NHTBE cell differentiation and that RA-inducible Sp1 plays a major role in up-regulating human CREB gene expression. This result implies that co-operation of these two transcription factors plays a crucial role in mediating early events of normal mucous cell differentiation of bronchial epithelial cells.

Poly(A)-binding protein-interacting protein 1 binds to eukaryotic translation initiation factor 3 to stimulate translation.

Poly(A)-binding protein (PABP) stimulates translation initiation by binding simultaneously to the mRNA poly(A) tail and eukaryotic translation initiation factor 4G (eIF4G). PABP activity is regulated by PABP-interacting (Paip) proteins. Paip1 binds PABP and stimulates translation by an unknown mechanism. Here, we describe the interaction between Paip1 and eIF3, which is direct, RNA independent, and mediated via the eIF3g (p44) subunit. Stimulation of translation by Paip1 in vivo was decreased upon deletion of the N-terminal sequence containing the eIF3-binding domain and upon silencing of PABP or several eIF3 subunits. We also show the formation of ternary complexes composed of Paip1-PABP-eIF4G and Paip1-eIF3-eIF4G. Taken together, these data demonstrate that the eIF3-Paip1 interaction promotes translation. We propose that eIF3-Paip1 stabilizes the interaction between PABP and eIF4G, which brings about the circularization of the mRNA.

Human TOB, an antiproliferative transcription factor, is a poly(A)-binding protein-dependent positive regulator of cytoplasmic mRNA deadenylation.

In mammalian cells, mRNA decay begins with deadenylation, which involves two consecutive phases mediated by the PAN2-PAN3 and the CCR4-CAF1 complexes, respectively. The regulation of the critical deadenylation step and its relationship with RNA-processing bodies (P-bodies), which are thought to be a site where poly(A)-shortened mRNAs get degraded, are poorly understood. Using the Tet-Off transcriptional pulsing approach to investigate mRNA decay in mouse NIH 3T3 fibroblasts, we found that TOB, an antiproliferative transcription factor, enhances mRNA deadenylation in vivo. Results from glutathione S-transferase pull-down and coimmunoprecipitation experiments indicate that TOB can simultaneously interact with the poly(A) nuclease complex CCR4-CAF1 and the cytoplasmic poly(A)-binding protein, PABPC1. Combining these findings with those from mutagenesis studies, we further identified the protein motifs on TOB and PABPC1 that are necessary for their interaction and found that interaction with PABPC1 is necessary for TOB's deadenylation-enhancing effect. Moreover, our immunofluorescence microscopy results revealed that TOB colocalizes with P-bodies, suggesting a role of TOB in linking deadenylation to the P-bodies. Our findings reveal a new mechanism by which the fate of mammalian mRNA is modulated at the deadenylation step by a protein that recruits poly(A) nuclease(s) to the 3' poly(A) tail-PABP complex.

Involvement of heparin-like glycosaminoglycans and expression of a novel heparan sulfate binding protein (p24) during human placentation and in a model for human implantation

Previous studies in our laboratory have indicated that heparan sulfate proteoglycans (HSPGs) play an important role in murine embryo implantation. To investigate the potential function of HSPGs in human implantation, two human cell lines (RL95 and JAR) were selected to model uterine epithelium and embryonal trophectoderm, respectively. A heterologous cell-cell adhesion assay showed that initial binding between JAR and RL95 cells is mediated by cell surface glycosaminoglycans (GAG) with heparin-like properties, i.e., heparan sulfate and dermatan sulfate. Furthermore, a single class of highly specific, protease-sensitive heparin/heparan sulfate binding sites exist on the surface of RL95 cells. Three heparin binding, tryptic peptide fragments were isolated from RL95 cell surfaces and their amino termini partially sequenced. Reverse transcription-polymerase chain reaction (RT-PCR) generated 1 to 4 PCR products per tryptic peptide. Northern blot analysis of RNA from RL95 cells using one of these RT-PCR products identified a 1.2 Kb mRNA species (p24). The amino acid sequence predicted from the cDNA sequence contains a putative heparin-binding domain. A synthetic peptide representing this putative heparin binding domain was used to generate a rabbit polyclonal antibody (anti-p24). Indirect immunofluorescence studies on RL95 and JAR cells as well as binding studies of anti-p24 to intact RL95 cells demonstrate that p24 is distributed on the cell surface. Western blots of RL95 membrane preparations identify a 24 kDa protein (p24) highly enriched in the 100,000 g pellet plasma membrane-enriched fraction. p24 eluted from membranes with 0.8 M NaCl, but not 0.6 M NaCl, suggesting that it is a peripheral membrane component. Solubilized p24 binds heparin by heparin affinity chromatography and $\sp{125}$I-heparin binding assays. Furthermore, indirect immunofluorescence studies indicate that cytotrophoblast of floating and attached villi of the human fetal-maternal interface are recognized by anti-p24. The study also indicates that the HSPG, perlecan, accumulates where chorionic villi are attached to uterine stroma and where p24-expressing cytotrophoblast penetrate the stroma. Collectively, these data indicate that p24 is a cell surface membrane-associated heparin/heparan sulfate binding protein found in cytotrophoblast, but not many other cell types of the fetal-maternal interface. Furthermore, p24 colocalizes with HSPGs in regions of cytotrophoblast invasion. These observations are consistent with a role for HSPGs and HSPG binding proteins in human trophoblast-uterine cell interactions. ^

The synthesis and application of a diazirine-modified uridine analogue for investigating RNA-protein interactions

The roles played by many ncRNAs remain largely unknown. Similarly, relatively little is known about the RNA binding proteins involved in processing ncRNA. Identification of new RNA/RNA binding protein (RBP) interactions may pave the way to gain a better understanding of the complex events occurring within cells during gene expression and ncRNA biogenesis. The development of chemical tools for the isolation of RBPs is of paramount importance. In this context, we report on the synthesis of the uridine phosphoramidite U Dz that bears a diazirine moiety on the nucleobase. RNA probes containing U Dz units were irradiated in the presence of single-stranded DNA binding protein (SSB), which is also known to bind ssRNAs, and shown to efficiently (15% yield) and selectively cross-link to the protein. The corresponding diazirine-modified uridine triphosphate U DzTP was synthesized and its capacity to act as a substrate for the T7 RNA polymerase was tested in transcription assays. U DzTP was accepted with a maximum yield of 38% for a 26mer RNA containing a single incorporation and 28% yield for triple consecutive incorporations. Thus, this uridine analogue represents a convenient biochemical tool for the identification of RNA binding proteins and unraveling the role and function played by ncRNAs.

The role of FUS in splicing regulation

Fused in sarcoma (FUS), also called translocated in liposarcoma (TLS), is a ubiquitously expressed DNA/RNA binding protein belonging to the TET family and predominantly localized in the nucleus. FUS is proposed to be involved in various RNA metabolic pathways including transcription regulation, nucleo-cytosolic RNA transport, microRNA processing or pre-mRNA splicing [1]. Mutations in the FUS gene were identified in patients with familial amyotrophic lateral sclerosis (ALS) type 6 and sporadic ALS [2, 3]. ALS, also termed Lou Gehrig's disease, is a fatal adult-onset neurodegenerative disease affecting upper and lower motor neurons in the brain and spinal cord. There is increasing evidence supporting the hypothesis that FUS might play an important role in pre-mRNA splicing regulation. Several splicing factors were identified to associate with FUS including hnRNPA2 and C1/C2 [4], Y-box binding protein 1 (YB-1) [5] and serine arginine (SR) proteins (SC35 and TASR) [6]. Additionally, FUS was identified as a constituent of human spliceosomal complexes [1]. Our recent results indicate that FUS has increased affinity for certain but not all snRNPs of the minor and major spliceosome. Furthermore, in vitro studies revealed that FUS directly interacts with a factor specific for one of those snRNPs. These findings might uncover the molecular mechanism by which FUS regulates splicing and could explain previously observed effects of FUS on the splicing of the adenovirus E1A minigene [7] and changes in splicing caused by ALS associated FUS mutations. [1] Lagier-Tourenne C et al. (2010) Human Molecular Genetics 19:46-64 [2] Kwiatkowski TJ Jr et al. (2009) Science 323:1205-8 [3] Vance C et al. (2009) Science 323:1208-11 [4] Zinser H et al. (1994) Genes Dev 8:2513-26 [5] Chansky, H.A., et al. (2001) Cancer Res. 61: 3586-90. [6] Yang L et al. (1998) J Biol Chem 273:27761-6 [7] Kino Y et al. (2010) Nucleic Acid Research 7:2781-2798

Proteomic characterization of the FUS/TLS interactome

FUS/TLS (fused in sarcoma/translocated in liposarcoma) is a ubiquitously expressed RNA-binding protein, that has been discovered as fused to transcription factors in several human sarcomas and found in protein aggregates in neurons of patients with an inherited form of Amyotrophic Lateral Sclerosis [1]. To date, FUS has been implicated in a variety of cellular processes such as gene expression control, transcriptional regulation, pre-mRNA splicing and miRNA processing [2]. In addition, some evidences link FUS to genome stability control and DNA damage response. In fact, mice lacking FUS are hypersensitive to ionizing radiation and show high levels of chromosome instability and in response to double-strand breaks, FUS gets phosphorylated by the protein kinase ATM [3, 4, 5]. Moreover, upon DNA damage stress, FUS mediates Ebp1 (ErbB3 receptor-binding protein) SUMOylation, a post-translational modification that is required for its onco-suppressive activity, by acting as SUMO E3 ligase [6]. The study aims to investigate the role of FUS in DNA damage response and SUMOylation, two cellular pathways tightly interconnected to each other. Moreover, we will exploit biochemical and mass spectrometry-based approaches in order to identify other potential substrates of the E3 SUMO ligase activity of FUS. Preliminary results of mass spectrometric identification of FUS interacting proteins, in HEK293 and SHSY5Y cells, highlighted the interaction of FUS with several proteins involved in DNA damage response and many of those have been described already as target of SUMOylation, such as XRCC5, DDX5, PARP1, Nucleophosmin, and others. These evidences strengthen the hypothesis that FUS might represent a link between these pathways, even thou its exact role still needs to be clearly addressed. [1] Vance C. et al. (2009) Science 323(5918): p. 1208-11 [2] Fiesel FC., Kahle PJ. (2011) FEBS J. 278(19): p. 3550-68 [3] Kuroda M. et al. (2000) Embo J. 19(3): p. 453-62 [4] Hicks GG. et al. (2000) Nat Genet. 24(2):p. 175-9 [5] Gardiner M. et al. (2008) Biochem J. 415(2): p. 297-307 [6] Oh SM. et al. (2010) Oncogene 29(7): p. 1017-30