HemK2 functions for sufficient protein synthesis and RNA stability through eRF1 methylation duringDrosophilaoogenesis

Abstract

AbstractHemK2 is a highly conserved methyltransferase spanning from yeast to humans. Despite its conservation, the identification of its genuine substrates has been controversial, and its biological importance in higher organisms remains unclear. In this study, we elucidate the role of HemK2 in the methylation of eukaryotic Release Factor 1 (eRF1), a process essential for female germline development inDrosophila melanogaster. Knockdown ofhemK2in the germline cells (hemK2-GLKD) induces apoptosis in these cells, accompanied by a pronounced decrease in both eRF1 methylation and protein synthesis. The overexpression of a methylation-deficient eRF1 variant recapitulates the defects observed inhemK2-GLKD, suggesting that eRF1 is a primary methylation target of HemK2. Furthermore,hemK2-GLKD leads to significant reduction mRNA levels in germline cell. We demonstrate that these defects in oogenesis and protein synthesis can be partially restored by inhibiting the No-Go Decay pathway. In addition,hemK2knockdown is associated with increased disome formation, suggesting that disruptions in eRF1 methylation may provoke ribosomal stalling, which subsequently activates translation-coupled mRNA surveillance mechanisms that degrade actively-translated mRNAs. We propose that HemK2-mediated methylation of eRF1 is critical for ensuring efficient protein production and mRNA stability, which are vital for the generation of high-quality eggs.