Identification Of New Phosphorylation Sites In Rbm38 And Primary Research Of Its Function

Cancer is a worldwide disease that threatens the health of human beings.How to prevent and treat cancer has become a research hotspot.Rbm38?RNA binding motif protein38?is an important cancer-associated RNA-binding protein that is involved in the post-transcriptional regulation of many cancer genes,including the p53 family,and plays a key regulatory role in the proliferation and senescence of many cancer cells.In our study,we found two novel phosphorylation sites in Rbm38:a serine at X-th position?SerX?,and a threonine at Y-th position?ThrY?.To study the biological function of SerX,we designed a phosphorylated antibody against this site and found that Rbm38 can dimerize after SerX phosphorylation.We have validated A-Raf as the phosphorylation kinase of Rbm38 SerX via the analysis of protein interaction mass spectrometry.A-Raf is also a cancer-associated protein and a member of the Raf?Rapidly Accelerated Fibrosarcoma?family,which participates in the MAPK?mitogen-activated protein kinase?pathway.We have also found that metal ion Zn²⁺promotes the phosphorylation and dimerization of Rbm38,but in vitro experiments have shown that in the presence of A-Raf,Rbm38 can dimerize without Zn²⁺.We found that the dimeric Rbm38 is mainly distributed in the nucleus,while its monomer is distributed in the cytoplasm.We found that the nuclear transport protein Cse1l is involved in the transportation of the dimeric Rbm38 between the nuclear and cytoplasm.Furthermore,we found that DNA damage activates Rbm38 SerX phosphorylation,causing its aggregation in the nucleus.Therefore,we speculate that SerX phosphorylated Rbm38can participate in the direct repair of DNA damage or the regulation of related genes after entering the nucleus.We have successfully constructed a mutated mouse strain that will further assist in revealing the function of Rbm38 phosphorylation from animal levels in the future.