Mutant of RNA Binding Protein Zc3h14 Causes Cell Growth Delay/Arrest through Inducing Multinucleation and DNA Damage

ZC3H14 proteins bind poly (A) tail of RNAs through the CCCH (5) zinc finger domain, shuttle between the nucleus and the cytoplasm, and play roles in nuclear exporting and proper polyadenylation of mRNA transcripts. However, molecular and cellular mechanisms of mammalian ZC3H14 remain largely unknown. Here we identified the mouse Zc3h14 gene and its encoded Zc3h14 protein. We found that Mouse Zc3h14 gene had at least two transcript isoforms, both were widely expressed in various tissues. Mouse ZC3H14 protein had one N-terminus Q-rich domain and one CCCH (5) zinc fingers domain. Both the two isoforms localized to the nucleus, and intriguingly, formed multiple nuclear speckles. We mapped the core nuclear localization signal to 292-RKRK sequences. Serial mutation analysis showed that the CCCH (5) zinc fingers domain was necessary but not sufficient for nuclear speckle formation. Over-expression of CCCH(5) domain as a dominant negative mutant, caused dramatic cell cycle delay, accompanied with multiple morphological abnormalities, such as long processes growing-out, multinucleation, and nuclear fragmentation. Further studies demonstrated that the CCCH (5) domain induced nuclear foci formation of the DNA damage marker g-H2AX. RT-PCR analysis showed that a group of DNA damage/repair genes, such as Cdk2, Ddb1, Mdm2, p21, p53, Rad50, as well as two RNA binding proteins, Pabpc1 and Rbm10, were dramatically up-regulated. Immunoprecipitation and mass spectrometry analysis further showed that the CCCH (5) domain could bind with RNA binding protein RBM10 in an RNA-dependent manner, and the CCCH (5) domain could also immunoprecipitate a group of chromatin stability/DNA damage-related proteins. In brief, our data for the first time demonstrated that the RNA binding protein, ZC3H14, is associated with genome/chromatin stability and DNA damage/repair.