Role of nuclear O-GalNAc glycosylation in CHO cells

IRAZOQUI, FJ; GARAY, YC

Mendoza, Argentina

Congreso; SAIB; 2022

Epigenetics represents chemical and covalent modifications that can take place on DNA and nuclear proteins without modifying the sequence of these molecules, which have a key role in the physiology of DNA, such as in regulation of gene transcription. Previously, we and other groups around the world have shown that O-GalNAc glycosylation, one of the most important post-translational modifications, is occurring in proteins of the cell nucleus, in addition to Golgi apparatus. Using CHO ldlD cells as experimental model, which does not have the ability to synthesize UDP-GalNAc, we study the nuclear role of O-GalNAc glycosylation in CHO cells. The presence of polypeptide GalNAc-transferase 3 isoform was observed in cell nucleus by Z stack methodology (IF). Using VVL lectin, we demonstrated terminal Tn (GalNAcαSer/Thr) residues with nuclear localization. O-GalNAc glycan sites of CHO nuclear proteins were identified in key nuclear proteins of cell physiology. Through mass spectrometry (proteomics) we were able to detect that CHO ldlD with enhanced nuclear O-GalNAc glycosylation (as consequence of GalNAc in cell culture) modified the expression level of multiple cellular proteins. These results are a significant contribution on insight the nuclear O-GalNAc glycan roles in the regulation of protein expression. In addition, the nuclear O-GalNAc glycosylation affected the rate of cell proliferation. Nuclear proteins of CHO cells that are modified by terminal O-GalNAc residues (such as histones and transcription factors) have already been described before, so this change in protein expression may be due to control of gene transcription mediated by O-GalNAc glycosylation.