eEF1Bγ binds the Che-1 and TP53 gene promoters and their transcripts

Background: We have previously shown that the eukaryotic elongation factor subunit 1B gamma (eEF1B gamma) interacts with the RNA polymerase II (pol II) alpha-like subunit C (POLR2C), alone or complexed, in the pol II enzyme. Moreover, we demonstrated that eEF1B gamma binds the promoter region and the 3' UTR mRNA of the vimentin gene. These events contribute to localize the vimentin transcript and consequentially its translation, promoting a proper mitochondrial network. Methods: With the intent of identifying additional transcripts that complex with the eEF1B gamma protein, we performed a series of ribonucleoprotein immunoprecipitation (RIP) assays using a mitochondria-enriched heavy membrane (HM) fraction. Results: Among the eEF1B gamma complexed transcripts, we found the mRNA encoding the Che-1/AATF multifunctional protein. As reported by other research groups, we found the tumor suppressor p53 transcript complexed with the eEF1B gamma protein. Here, we show for the first time that eEF1B gamma binds not only Che-1 and p53 transcripts but also their promoters. Remarkably, we demonstrate that both the Che-1 transcript and its translated product localize also to the mitochondria and that eEF1B gamma depletion strongly perturbs the mitochondrial network and the correct localization of Che-1. In a doxorubicin (Dox)-induced DNA damage assay we show that eEF1B gamma depletion significantly decreases p53 protein accumulation and slightly impacts on Che-1 accumulation. Importantly, Che-1 and p53 proteins are components of the DNA damage response machinery that maintains genome integrity and prevents tumorigenesis. Conclusions: Our data support the notion that eEF1B gamma, besides its canonical role in translation, is an RNA-binding protein and a key player in cellular stress responses. We suggest for eEF1B gamma a role as primordial transcription/translation factor that links fundamental steps from transcription control to local translation.