Nutrient-driven O-GlcNAcylation of key components of the transcription machinery may epigenetically modulate gene expression in metazoans. The global effects of GlcNAcylation on transcription can be addressed directly in C. elegans because knockouts of the O-GlcNAc cycling enzymes are viable and fertile. Using anti-O-GlcNAc ChIP-on-chip whole-genome tiling arrays on wild-type and mutant strains, we detected over 800 promoters where O-GlcNAc cycling occurs, including microRNA loci and multigene operons. Intriguingly, O-GlcNAc-marked promoters are biased toward genes associated with PIP3 signaling, hexosamine biosynthesis, and lipid/carbohydrate metabolism. These marked genes are linked to insulin-like signaling, metabolism, aging, stress, and pathogen-response pathways in C. elegans . Whole-genome transcriptional profiling of the O-GlcNAc cycling mutants confirmed dramatic deregulation of genes in these key pathways. As predicted, the O-GlcNAc cycling mutants show altered lifespan and UV stress susceptibility phenotypes. We propose that O-GlcNAc cycling at promoters participates in a molecular program impacting nutrient-responsive pathways in C. elegans , including stress, pathogen response, and adult lifespan. The observed impact of O-GlcNAc cycling on both signaling and transcription in C. elegans has important implications for human diseases of aging, including diabetes and neurodegeneration.

Background: Modifications of the RNA polymerase II CTD are necessary for transcriptional regulation. Results: Perturbation of O-GlcNAc addition and removal showed transcription defects in vitro and in vivo. Conclusion: O-GlcNAc modification of the CTD functions in transcription initiation.Significance: These data provide an additional modification of the CTD that acts before the initiation of transcription.

In a variety of organisms, including worms, flies, and mammals, glucose homeostasis is maintained by insulin-like signaling in a robust network of opposing and complementary signaling pathways. The hexosamine signaling pathway, terminating in O-linked-N-acetylglucosamine (O-GlcNAc) cycling, is a key sensor of nutrient status and has been genetically linked to the regulation of insulin signaling in Caenorhabditis elegans. Here we demonstrate that O-GlcNAc cycling and insulin signaling are both essential components of the C. elegans response to glucose stress. A number of insulin-dependent processes were found to be sensitive to glucose stress, including fertility, reproductive timing, and dauer formation, yet each of these differed in their threshold of sensitivity to glucose excess. Our findings suggest that O-GlcNAc cycling and insulin signaling are both required for a robust and adaptable response to glucose stress, but these two pathways show complex and interdependent roles in the maintenance of glucose-insulin homeostasis.

We have studied the role of nuclear factor of activated T-cells (NFAT) transcription factors in the induction of vascular smooth muscle cell (VSMC) growth by platelet-derived growth factor-BB (PDGF-BB) and thrombin, the receptor tyrosine kinase (RTK) and G-protein-coupled receptor (GPCR) agonists, respectively. NFATc1 but not NFATc2 or NFATc3 was translocated from the cytoplasm to the nucleus upon treatment of VSMCs with PDGF-BB or thrombin. Translocation of NFATc1 was followed by an increase in NFAT-DNA binding activity and NFAT-dependent reporter gene expression. Cyclosporin A (CsA), a potent and specific inhibitor of calcineurin, a calcium/calmodulin-dependent serine phosphatase involved in the dephosphorylation and activation of NFATs, blocked NFAT-DNA binding activity and NFAT-dependent reporter gene expression induced by PDGF-BB and thrombin. CsA also completely inhibited PDGF-BB- and thrombin-induced VSMC growth, as measured by DNA synthesis and cell number. In addition, forced expression of the NFAT-competing peptide VIVIT for calcineurin binding significantly attenuated the DNA synthesis induced by PDGF-BB and thrombin in VSMCs. Together, these findings for the first time demonstrate a role for NFATs in RTK and GPCR agonist-induced growth in VSMCs.

CtBP (C-terminal binding protein) is an evolutionarily conserved NAD(H)-dependent transcriptional corepressor, whose activity has been shown to be regulated by the NAD/NADH ratio. Although recent studies have provided significant new insights into mechanisms by which CtBP regulates transcription, the biological function of CtBP remains incompletely understood. Here, we report that genetic inactivation of the Caenorhabditis elegans homolog, ctbp-1, results in life span extension, which is suppressed by reintroduction of the ctbp-1 genomic DNA encoding wild-type but not NAD(H)-binding defective CTBP-1 protein. We show that CTBP-1 possibly modulates aging through the insulin/IGF-1 signaling pathway, dependent on the forkhead transcription factor DAF-16, but independent of the NAD-dependent histone deacetylase SIR-2.1. Genome-wide microarray analysis identifies >200 potential CTBP-1 target genes. Importantly, RNAi inhibition of a putative triacylglycerol lipase gene lips-7(C09E8.2) but not another lipase suppresses the life span extension phenotype. Consistently, metabolic analysis shows that the triacylglycerol level is reduced in the ctbp-1 deletion mutant, which is restored to the wild-type level by RNAi inhibition of lips-7. Taken together, our data suggest that CTBP-1 controls life span probably through the regulation of lipid metabolism.aging ͉ CtBP ͉ transcription corepressor C tBP is a transcriptional corepressor that is evolutionarily conserved from Caenorhabditis elegans to human (1). CtBP shares sequence homology with the NAD/NADH-dependent 2-hydroxy acid dehydrogenases (2-Hacid DH) (2), and has been shown to exhibit dehydrogenase activity in vitro (3-5), although the physiological substrates and functional significance of this enzymatic activity remain unclear. CtBP binds NAD and NADH, and the NAD/NADH ratio appears to regulate the interactions of CtBP with DNA-binding transcription factors (6, 7), suggesting a potential role for CtBP as a sensor of cellular redox states. CtBP represses transcription by recruiting multiple histone modifying enzymes including the histone H3 lysine 9 (H3K9) methyltransferase G9a/HMTase1 and the histone H3 lysine 4 (H3K4) demethylase LSD1 (3,8). Previous studies suggest a role for CtBP in mouse development, apoptosis, and hypoxia-induced tumor migration (9-12). However, by and large, the biology of CtBP is still incompletely understood.Aging is a complex process regulated by an interacting network of factors. The insulin/insulin-like growth factor-1 (IGF-1) signaling pathway, the JNK anti-stress pathway and the mitochondria respiratory chain, have all been shown to regulate the aging process (13). Besides genetic factors, environmental conditions including stress and nutrient availability, have also been demonstrated to influence longevity (13-15). Transcription factors including DAF-16 and the NAD-dependent histone deacetylase SIR2 are at the converging points to integrate these different signals and regulate longevity through modulating gene transcription (13,15). Similar...

Killing by Entamoeba histolytica requires parasite adherence to host galactose-and N-acetyl-D-galactosamine (Gal/GalNAc)-containing cell surface receptors. A 260-kDa heterodimeric E. histolytica Gal/GalNAc lectin composed of heavy (Hgl) and light (Lgl) subunits has been previously described. Here we present the cloning and characterization of Igl, a 150-kDa intermediate subunit of the Gal/GalNAc lectin. Igl, Hgl, and Lgl colocalized on the surface membrane of trophozoites. Two unlinked copies of genes encoding Igl shared 81% amino acid sequence identity (GenBank accession no. AF337950 and AF337951). They encoded cysteine-rich proteins with amino-and carboxy-terminal hydrophobic signal sequences characteristic of glycosylphosphatidylinositol (GPI)-anchored membrane proteins. The igl genes lacked carbohydrate recognition domains but were members of a large family of amebic genes containing CXXC and CXC motifs. These data indicate that Igl is part of the parasite's multimolecular Gal/GalNAc adhesin required for host interaction.Carbohydrate-protein interactions initiate the contact-dependent cytotoxicity for which Entamoeba histolytica was named. Parasite recognition of host galactose (Gal) and Nacetyl-D-galactosamine (GalNAc) residues initiates trophozoite adherence to human colonic mucin, colonic epithelium, neutrophils and erythrocytes, certain bacteria, and a variety of cultured cell lines (3-7, 16, 19-22, 27, 36-38). Contact-dependent killing of target cells is Ͼ90% inhibited by Gal and GalNAc (34,37,41). Additionally, Chinese hamster ovary (CHO) cell glycosylation-deficient mutants lacking terminal Gal/GalNAc residues on N-and O-linked sugars are nearly totally resistant to amebic adherence and cytolytic activity (23,24,39).The E. histolytica 260-kDa Gal/GalNAc lectin is a heterodimer of transmembrane heavy (170 kDa) (Hgl) and GPIanchored light (35 or 31 kDa) (Lgl) glycoproteins linked by disulfide bonds. It was originally identified by galactose affinity chromatography and with adherence-inhibitory monoclonal antibodies (MAbs) (30,43). Both Hgl and Lgl are encoded by gene families (28,35). Antibodies that block or augment parasite Gal/GalNAc binding activity map to the cysteine-rich region (amino acids 356 to 1143) of Hgl (25), and this region (when expressed in Escherichia coli) contains a functional carbohydrate recognition domain (14, 33). The cytoplasmic tail of Hgl has homology to the cytoplasmic domain of ␤2 and ␤7 integrins, including regions implicated in binding of the intracellular signaling molecules Shc and Grb2. Overexpression of the cytoplasmic tail results in a dominant negative effect on endogenous lectin activity, with decreased adherence, cytotoxicity, and in vivo virulence (44).The 150-kDa lectin intermediate subunit (Igl) was originally identified as a trophozoite surface antigen recognized by MAbs which block trophozoite adherence to mammalian cells in vitro (9)(10)(11)42). The EH3015 MAb specific for Igl significantly inhibits adherence of amebae to erythrocytes and CHO cells, erythrop...

The pilin glycoprotein (PilE) is the main building block of the pilus of Neisseria gonorrhoeae (gonococcus [GC]). GC pilin is known to carry a disaccharide O-glycan, which has an αGal attached to the O-linked GlcNAc by a 1–3 glycosidic bond. In this report, we describe the cloning and characterization of the GC gene, pilus glycosyl transferase A (pgtA), which encodes the galactosyl transferase that catalyzes the synthesis of this Gal–GlcNAc bond of pilin glycan. A homopolymeric tract of Gs (poly-G) is present in the pgtA gene of many GC strains, and this pgtA with poly-G can undergo phase variation (Pv). However, in many other GC, pgtA lacks the poly-G and is expressed constitutively without Pv. Furthermore, by screening a large number of clinical isolates, a significant correlation was observed between the presence of poly-G in pgtA and the dissemination of GC infection. Poly-G was found in pgtA in all (24 out of 24) of the isolates from patients with disseminated gonococcal infection (DGI). In contrast, for the vast majority (20 out of 28) of GC isolated from uncomplicated gonorrhea (UG) patients, pgtA lacked the poly-G. These results indicate that Pv of pgtA is likely to be involved in the conversion of UG to DGI.

Discriminating pathogenic bacteria from bacteria used as a food source is key to Caenorhabidits elegans immunity. Using mutants defective in the enzymes of O-linked N-acetylglucosamine (O-GlcNAc) cycling, we examined the role of this nutrient-sensing pathway in the C. elegans innate immune response. Genetic analysis showed that deletion of O-GlcNAc transferase (ogt-1) yielded animals hypersensitive to the human pathogen S. aureus but not to P. aeruginosa. Genetic interaction studies revealed that nutrient-responsive OGT-1 acts through the conserved β-catenin (BAR-1) pathway and in concert with p38 MAPK (PMK-1) to modulate the immune response to S. aureus. Moreover, whole genome transcriptional profiling revealed that O-GlcNAc cycling mutants exhibited deregulation of unique stress- and immune-responsive genes. The participation of nutrient sensor OGT-1 in an immunity module evolutionarily conserved from C. elegans to humans reveals an unexplored nexus between nutrient availability and a pathogen-specific immune response.