Biosynthesis of O-GalNAc glycans in the human cell nucleus

GARAY, YOHANA C.; LORENZ, VIRGINIA; CEJAS, ROMINA B.; IRAZOQUI, FERNANDO J.

Buenos Aires

Simposio; 3rd Argentinian Symposium on Glycobiology; 2019

Biological functions of nuclear proteins are regulated by posttranslationalmodifications (PTMs) that modulate gene expression and cellular physiology. However, the role of O-linked glycosylation (O-GalNAc) as a PTM of nuclear proteins in the human cell has not been previously reported. Here, we examinedin detail the initiation of O-GalNAc glycan biosynthesis, representing a novel PTM of nuclear proteins, in the nucleus of human cells, with an emphasis on HeLa cells. Using soluble nuclear fractions from purified nuclei, enzymatic assays,fluorescence microscopy, affinity chromatography, mass spectrometry and FRET analyses, we identified all factors required for biosynthesis of O-GalNAc glycans in nuclei: the donor substrate (UDP-GalNAc), nuclear polypeptide GalNActransferase activity, and a GalNAc transferase (polypeptide GalNAc-T3). Moreover, we identified O-GalNAc glycosylated proteins in the nucleus and present solid evidence for O-GalNAc glycan synthesis in this organelle. The demonstration of OGalNAc glycosylation of nuclear proteins in mammalian cellsreported here has important implications for cell and chemical biology.