HemK class methyltransferase, a protein translation regulator: role in growth, development and phenotypic diversity

Across eukaryotic and prokaryotic life forms, translation termination occurs followed by disassembly of ribosomal subunits and release of the nascent polypeptide. This process is governed by the presence of Release factors or translation termination factors, which render polypeptide hydrolysis from the peptidyl t-RNA by interacting with its conserved GGQ motif. Studies have shown that methylation of Release Factors by Methyltransferases at this highly conserved motif is necessary for efficient translation termination; failure to do so leads to the accumulation of polyribosomes and subsequently altered protein synthesis, ultimately resulting in an undesired phenotype. HemK class methyltransferases are a widely conserved class of enzymes involved in the methylation of Glutamine. Due to methylation of release factors by HemK at the GGQ motif, faithful translation termination occurs. Its absence leads to reduced stress tolerance as well as developmental abnormalities and other detrimental effects. Studies have suggested HemK to be associated with DNA methylation as well as chromatin remodelling activities. This review provides a brief overview of the role of HemK as a translational as well as transcriptional regulator, and its function in prokaryotic and eukaryotic systems.