Abstract
Although mistranslation is commonly believed to be deleterious, recent evidence indicates that mistranslation can be actively regulated and be beneficial in stress response. Methionine mistranslation in mammalian cells is regulated by reactive oxygen species where cells deliberately alter the proteome through incorporating Met at non-Met positions to enhance oxidative stress response. However, it was not known whether specific, mistranslated mutant proteins have distinct activities from the wild-type protein whose sequence is restrained by the genetic code. Here, we show that Met mistranslation with and without Ca2+ overload generates specific mutant Ca2+/calmodulin-dependent protein kinase II (CaMKII) proteins substituting non-Met with Met at multiple locations. Compared to the genetically encoded wild-type CaMKII, specific mutant CaMKIIs can have distinct activation profiles, intracellular localization and enhanced phenotypes. Our results demonstrate that Met-mistranslation, or “Met-scan” can indeed generate mutant proteins in cells that expand the activity profile of the wild-type protein, and provide a molecular mechanism for the role of regulated mistranslation.
Highlights
It was commonly believed that translational fidelity is maintained at high levels in cells at all times, accumulating evidence indicates that mistranslation is regulated in cells, and mistranslation may broaden proteomic and phenotypic diversity to help cells respond to stress [1,2,3,4,5]
Methionine-mistranslation is a recently discovered phenomenon where mammalian cells deliberately mischarge non-Met-tRNAs with amino acid methionine in unstressed cells and in response to innate immune and chemically triggered oxidative stress. These mischarged tRNAs are used in translation to generate mutant proteins containing non-Met to Met substitutions
It was unknown whether any specific mutant proteins generated in mistranslation truly have distinct activities as the wild-type protein
Summary
It was commonly believed that translational fidelity is maintained at high levels in cells at all times, accumulating evidence indicates that mistranslation is regulated in cells, and mistranslation may broaden proteomic and phenotypic diversity to help cells respond to stress [1,2,3,4,5]. Met-mistranslation is derived from misacylating non-methionyl-tRNAs with the amino acid methionine. Numerous non-Met to Met-substituted mutant proteins have been identified by mass spectrometry [1,6,7] or through designed fluorescent protein [6], indicating that Met misacylated tRNAs are directly used in translation. The cellular phenotype conferred by Met-mistranslation is exerted through specific mutant proteins. It was not known whether any of the mutant proteins generated in Met-mistranslation has distinct activities compared to the wild-type protein
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