Serine 195 phosphorylation in the RNA-binding protein Rbm38 increases p63 expression by modulating Rbm38’s interaction with the Ago2–miR203 complex

Yanhong Zhang, Xiuli Feng, Wenqiang Sun, Jin Zhang, Xinbin Chen

Research output: Contribution to journalArticle

Abstract

The p63 transcription factor, a p53 family protein, regulates genes involved in various cellular processes, including cell growth and differentiation. We previously showed that RNA-binding motif protein (Rbm38) is a p63 target and, in turn, regulates p63 mRNA stability by binding to the AU/U-rich element in its 3UTR. Interestingly, Rbm38 can be phosphorylated at serine 195, altering its ability to regulate mRNA translation. However, whether the Ser-195 phosphorylation affects Rbm38’s ability to destabilize p63 mRNA remains unclear. Here, using MCF7 and HaCaT cells, we showed that ectopic expression of phosphomimetic Rbm38-S195D increases, whereas WT Rbm38 and nonphosphorylatable Rbm38-S195A decrease p63 protein and transcript levels. We also found that upon activation of glycogen synthase kinase 3 (GSK3), phosphorylation of Rbm38 at Ser-195 is increased, enhancing p63 expression in an Rbm38-dependent manner. To confirm this, we generated mouse embryo fibroblasts (MEFs) in which Ser-193 in mouse Rbm38 (equivalent to Ser-195 in human Rbm38) was substituted with aspartic acid (Rbm38 S193D/S193D ) or alanine (Rbm38 S193A/S193A ). We observed that the p63 transcript level was increased in Rbm38 S193D/S193D MEFs, but decreased in Rbm38 S193A/S193A MEFs. Mechanistically, we found that WT Rbm38, but not Rbm38-S195D, is required for p63 mRNA degradation mediated by microRNA 203 (miR203). Furthermore, we noted that Argonaute 2 (Ago2), a key regulator in microRNA-mediated mRNA decay, associates with WT Rbm38, and this association was reduced by Ser-195 phosphorylation. Together, our results reveal a critical mechanism by which Ser-195 phosphorylation in Rbm38 increases p63 expression by attenuating the association of Rbm38 with the Ago2–miR203 complex.

Original languageEnglish (US)
Pages (from-to)2449-2459
Number of pages11
JournalJournal of Biological Chemistry
Volume294
Issue number7
DOIs
StatePublished - Jan 1 2019

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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