Autoregulation of YB-1 protein synthesis in cells

Y-box binding protein 1 (YB-1) regulates key cellular processes including transcription, translation, and DNA repair through interactions with nucleic acids and multiple protein partners. Its multifunctionality makes control of YB-1 levels critical for cellular homeostasis and adaptation to stress. YB-1 synthesis regulation occurs through gene transcription, protein stability (mediated by long noncoding RNAs), and translation of its mRNA. Autoregulation of YB-1 mRNA translation remains a controversial topic of research. Early in vitro studies pointed to a role for the 5′ untranslated region (UTR) in inhibiting protein synthesis, but other studies have demonstrated the importance of YB-1 binding to the 3′ UTR in translation repression. The controversy is compounded by the lack of confirmation of these mechanisms in cell cultures. Here, we demonstrate for the first time that YB-1 represses its own synthesis in cultured human cells. Using metabolic protein labeling and immunoprecipitation, we confirmed the effect of YB-1 on the translation of its mRNA. Experiments with reporter constructs showed that both untranslated regions of YB-1 mRNA are required for autoregulation, resolving contradictions existing in the literature. These results highlight a complex mechanism for the control of YB-1 levels, combining elements of the 5′ and 3′ UTRs of mRNA, and confirm their role in fine-tuning B-1 synthesis.