LAUSR

Abstract The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is a major pre‐mRNA binding protein involved in transcription and translation. Although predominantly nuclear, hnRNP A1 shuttles rapidly between the nucleus and the cytosol, delivering its anchored pre‐mRNA for further processing. Translocation is important for hnRNP A1 to accomplish its transcriptional and translational roles. Transportin1 (Trn1), a translocation protein, facilitates the translocation of hnRNP A1 back to the nucleus. Moreover, phosphorylation of serine residues at hnRNP A1 C‐terminal domain affects its translocation. In this study, we found that phosphorylation is not the only modification that hnRNP A1 undergoes, but also O‐linked N‐acetylglucosaminylation (O‐GlcNAcylation) could occur. Several putative novel O‐GlcNAcylation and phosphorylation sites in hnRNP A1 were mapped. Whereas enhanced O‐GlcNAcylation increased hnRNP A1 interaction with Trn1, enhanced phosphorylation reduced the interaction between the proteins. In addition, elevated O‐GlcNAcylation resulted in hnRNP A1 seclusion in the nucleus, whereas elevated phosphorylation resulted in its accumulation in the cytosol. These findings suggest that a new player, i.e., O‐GlcNAcylation, regulates hnRNP A1 translocation and interaction with Trn1, possibly affecting its function. There is a need for further study, to elucidate the role of O‐GlcNAcylation in the regulation of the specific activities of hnRNP A1 in transcription and translation. HighlightsO‐GlcNAcylation regulates hnRNP A1 translocation and interaction with Trn1.Reciprocity between phosphorylation and O‐GlcNAcylation in hnRNP A1 is proposed.Novel O‐GlcNAcylation and phosphorylation sites on hnRNPA1 were identified.