CE44 - Biochimie du Vivant

Transcription pre-initiation complex regulation by nutrient dependent O-GlcNAcylation of TATA-Box Binding Protein – TaNGoT

Submission summary

Gene expression is performed by three RNA polymerases (RNAPs) each of which is devoted to a specific class of gene. Assembly of specific molecular complexes at gene promoters to form pre-initiation complexes (PICs) ensure recruitment and positioning of the correct RNAP. Among the variety of factors necessary to form a functional PIC, the TATA-Box Binding Protein (TBP) has been considered as a common universally conserved platform for PIC assembly with a passive role in gene expression regulation. However, our recent data showed that TBP is a key player in the dynamic regulation of transcription initiation and that it is dynamically modified by O-GlcNAcylation at T114, T126 and S158. O-GlcNAcylation is a finely tuned post-translational modification of nucleocytoplasmic protein controlled by two unique enzymes. The O-GlcNAc transferase adds the sugar whereas O-GlcNAcase removes it. O-GlcNAcylation dynamically regulates activities of molecular players virtually involved in all cellular processes ranging from cell signaling, metabolism, epigenetics and transcription. It is now clear that O-GlcNAcylation plays critical roles in nutrient and stress regulation of nearly all aspects of cellular physiology. A growing body of evidence places O-GlcNAcylation at the nexus of nutritional status, cellular homeostasis, and the establishment of chronic diseases beyond those typically referred to as metabolic-related pathologies.
We previously showed that TBP T114-O-GlcNAcylation is involved in the formation of the B-TFIID complex, hence the dynamic association of TBP to chromatin and TBP promoter redistribution. In terms of cellular physiology, the glycosylation of TBP at T114 regulates a set of genes involved in lipid metabolism. Yet, the primary roles of T126 and S158 O-GlcNAcylation remain unknown but our preliminary data suggest that they could potentially be involved in the regulation/assembly of the PICs requested for transcription initiation by RNAPI, RNAPII and/or RNAPIII. Literature shows that alternative assembly of PICs allows targeting of specific core promoter elements, transcription of a subset of genes, and dynamism of transcription initiation by RNAPs. Therefore, site-specific O-GlcNAcylation of TBP may have a profound impact on cell transcriptome and cell physiology. Here, I propose to document the site-specific function of these residues, using combined transcriptomic and proteomic approaches on CRISPR-edited cell lines along with structure conformation and DNA-bending activity studies. Phenotypes of the CRISPR-edited cell lines will be further investigated to link the role of each O-GlcNAcylation site of TBP on cell physiology to the underlying molecular mechanism. Overall, TaNGoT ambitions to 1) understand the role of the TBP regulation by O-GlcNAcylation on transcription initiation and its impact on cell physiology, 2) decipher the O-GlcNAcylation site-specific functions onto the assembly of the PICs, 3) unveil the intrinsic molecular mechanism of this regulation. The outcome of TaNGoT will update the dogma of TBP as a mere platform by describing the molecular mechanism of regulation of basal transcription machinery by O-GlcNAcylation of TBP, highlighting an “O-GlcNAc code” of TBP.

Project coordinator

Monsieur Stéphan Hardivillé (UMR 8576 - Unité de glycobiologie structurale et fonctionnelle)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

UGSF UMR 8576 - Unité de glycobiologie structurale et fonctionnelle

Help of the ANR 299,217 euros
Beginning and duration of the scientific project: September 2021 - 48 Months

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