Functional genomic profiling of O-GlcNAc reveals its context-specific interplay with RNA polymerase II

Area of Science:

• Molecular Biology
• Epigenetics
• Glycobiology

Background:

• The role of reversible protein glycosylation in gene transcription is poorly understood.
• O-linked β-N-acetylglucosamine (O-GlcNAc) is the sole known glycosylation of nuclear proteins, including RNA polymerase II (RNA Pol II) and transcription factors.
• The regulatory function of O-GlcNAc in mammalian chromatin is unclear.

Purpose of the Study:

• To investigate the genomic distribution and regulatory role of O-GlcNAc modification in mammalian transcription.
• To explore the interplay between O-GlcNAc modification and the RNA Pol II transcription machinery.

Main Methods:

• Genome-wide profiling of O-GlcNAc-modified proteins.
• Perturbation of intracellular glycosylation and RNA Pol II degradation.
• Super-resolution microscopy.
• Intersection with public ChIP-seq datasets.

Main Results:

• O-GlcNAc-modified proteins are distributed non-randomly across the genome, enriched in heterochromatin and active gene promoters.
• O-GlcNAc modification generally promotes transcription of cellular genes, with O-GlcNAc Transferase (Ogt) knockdown leading to gene downregulation.
• RNA Pol II depletion alters O-GlcNAc levels at specific promoter sets, indicating a reciprocal relationship.

Conclusions:

• This study provides a detailed genomic map of O-GlcNAc-modified proteins in human and murine cells.
• A context-specific, reciprocal functional relationship exists between the transcription machinery and O-GlcNAc modification.