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
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Mentions: We next investigated whether arginine methylation of hnRNPK interferes with Ser302 phosphorylation. To this end, we generated M-GST-K, a recombinant GST-hnRNPK fusion protein carrying pre-methylated arginines, in E. coli as described in the ‘Materials and Methods’ section. The pre-methylation of this M-GST-K was verified using a methyl arginine-specific antibody, and the control GST-K showed no methylation signal (Figure 5a). Next, we performed the in vitro phosphorylation of pre-methylated M-GST-K and the un-methylated control (GST-K) using constitutively active PKCδ (catalytic fragment, CF-PKCδ) in the presence of [γ-32P]-ATP. A comparison of the phosphorylation levels showed that GST-K exhibited higher phosphorylation levels than M-GST-K (Figure 5b), suggesting that the pre-methylation of hnRNPK suppressed subsequent PKCδ-mediated phosphorylation in vitro.
Affiliation: Department of Life Sciences and Institute of Genome Sciences, National Yang Ming University, Taipei 11221, Taiwan.