Arginine methylation of hnRNPK negatively modulates apoptosis upon DNA damage through local regulation of phosphorylation.
Bottom Line: In addition, increased hnRNPK expression has been associated with tumor development and progression.In the present study, we demonstrated that the methylation of two essential arginines, Arg296 and Arg299, on hnRNPK inhibited a nearby Ser302 phosphorylation that was mediated through the pro-apoptotic kinase PKCδ.While such elevated apoptosis can be diminished through addition with wild-type hnRNPK, we further demonstrated that this increased apoptosis occurred through both intrinsic and extrinsic pathways and was p53 independent, at least in part.
Affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang Ming University, Taipei 11221, Taiwan.Show MeSH
Related in: MedlinePlus
Mentions: HnRNPK is highly abundant in cells, and its gene knockout is lethal in several species (1,50–52). In addition, the aggressive knockdown of endogenous hnRNPK in cells leads to cell death (12,21–23). To investigate the putative function of Arg296/Arg299 methylation of hnRNPK in vivo, we first overexpressed exogenous hnRNPK carrying diverse arginine mutations in U2OS cells. However, an insignificant phenotype was observed, likely reflecting the abundant presence of endogenous hnRNPK. We thus further established stable cell lines expressing exogenous WT hnRNPK or hnRNPK-2RK (R296K/R299K) and knocked down endogenous hnRNPK through lentivirus-based RNA interference, as described in the ‘Materials and Methods’ section. The resulting cells, U2OS-K-WT and U2OS-K-2RK cells, expressed a significant amount of exogenous hnRNPK-WT or hnRNPK-2RK over the endogenous hnRNPK (Figure 7a). Despite the arginine mutations in hnRNPK, the growth rate and morphology of these two cell lines were nearly identical (data not shown).
Affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang Ming University, Taipei 11221, Taiwan.