Hijacking of the O-GlcNAcZYME complex by the HTLV-1 Tax oncoprotein facilitates viral transcription

• Published in: PLoS pathogens 2017-07, Vol.13 (7), p.e1006518-e1006518
• Main Authors: Groussaud, Damien, Khair, Mostafa, Tollenaere, Armelle I, Waast, Laetitia, Kuo, Mei-Shiue, Mangeney, Marianne, Martella, Christophe, Fardini, Yann, Coste, Solène, Souidi, Mouloud, Benit, Laurence, Pique, Claudine, Issad, Tarik
• Format: Article
• Language: English
• Subjects: Acetylglucosamine - metabolism; beta-N-Acetylhexosaminidases - genetics; beta-N-Acetylhexosaminidases - metabolism; Biology and Life Sciences; Biotechnology; Co authorship; Cyclic AMP response element-binding protein; Cyclic AMP Response Element-Binding Protein - genetics; Cyclic AMP Response Element-Binding Protein - metabolism; Dimers; Enzymes; Gene expression; Gene Expression Regulation, Viral; Gene Products, tax - genetics; Gene Products, tax - metabolism; Genetic aspects; Host-Pathogen Interactions; HTLV-I (Virus); HTLV-I Infections - enzymology; HTLV-I Infections - genetics; HTLV-I Infections - metabolism; HTLV-I Infections - virology; Human T-lymphotropic virus 1 - genetics; Human T-lymphotropic virus 1 - metabolism; Humans; Insulin; Leukemia; Life Sciences; Lymphocytes; Lymphocytes T; Medicine and Health Sciences; N-Acetylglucosamine; N-Acetylglucosaminyltransferases - genetics; N-Acetylglucosaminyltransferases - metabolism; O-GlcNAcylation; Oncoproteins; Pharmacology; Phosphorylation; Physical Sciences; Physiological aspects; Post-translation; Post-translational modifications; Protein Processing, Post-Translational; Proteins; Recruitment; Regulatory sequences; Research and Analysis Methods; Serine; Social Sciences; T cells; T-Lymphocytes - enzymology; T-Lymphocytes - metabolism; T-Lymphocytes - virology; Tax protein; Threonine; Transcription; Transcription (Genetics); Transcription, Genetic; Viruses
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1006518

The viral Tax oncoprotein plays a key role in both Human T-cell lymphotropic virus type 1 (HTLV-1)-replication and HTLV-1-associated pathologies, notably adult T-cell leukemia. Tax governs the transcription from the viral 5'LTR, enhancing thereby its own expression, via the recruitment of dimers of phosphorylated CREB to cAMP-response elements located within the U3 region (vCRE). In addition to phosphorylation, CREB is also the target of O-GlcNAcylation, another reversible post-translational modification involved in a wide range of diseases, including cancers. O-GlcNAcylation consists in the addition of O-linked-N-acetylglucosamine (O-GlcNAc) on Serine or Threonine residues, a process controlled by two enzymes: O-GlcNAc transferase (OGT), which transfers O-GlcNAc on proteins, and O-GlcNAcase (OGA), which removes it. In this study, we investigated the status of O-GlcNAcylation enzymes in HTLV-1-transformed T cells. We found that OGA mRNA and protein expression levels are increased in HTLV-1-transformed T cells as compared to control T cell lines while OGT expression is unchanged. However, higher OGA production coincides with a reduction in OGA specific activity, showing that HTLV-1-transformed T cells produce high level of a less active form of OGA. Introducing Tax into HEK-293T cells or Tax-negative HTLV-1-transformed TL-om1 T cells is sufficient to inhibit OGA activity and increase total O-GlcNAcylation, without any change in OGT activity. Furthermore, Tax interacts with the OGT/OGA complex and inhibits the activity of OGT-bound OGA. Pharmacological inhibition of OGA increases CREB O-GlcNAcylation as well as HTLV-1-LTR transactivation by Tax and CREB recruitment to the LTR. Moreover, overexpression of wild-type CREB but not a CREB protein mutated on a previously described O-GlcNAcylation site enhances Tax-mediated LTR transactivation. Finally, both OGT and OGA are recruited to the LTR. These findings reveal the interplay between Tax and the O-GlcNAcylation pathway and identify new key molecular actors involved in the assembly of the Tax-dependent transactivation complex.