YB-1 Autoregulates Translation of Its Own mRNA at or prior to the Step of 40S Ribosomal Subunit Joining

Abstract

YB-1 is a member of the numerous families of proteins with an evolutionary ancient cold-shock domain. It is involved in many DNA- and RNA-dependent events and regulates gene expression at different levels. Previously, we found a regulatory element within the 3′ untranslated region (UTR) of YB-1 mRNA that specifically interacted with YB-1 and poly(A)-binding protein (PABP); we also showed that PABP positively affected YB-1 mRNA translation in a poly(A) tail-independent manner (O. V. Skabkina, M. A. Skabkin, N. V. Popova, D. N. Lyabin, L. O. Penalva, and L. P. Ovchinnikov, J. Biol. Chem. 278:18191-18198, 2003). Here, YB-1 is shown to strongly and specifically inhibit its own synthesis at the stage of initiation, with accumulation of its mRNA in the form of free mRNPs. YB-1 and PABP binding sites have been mapped on the YB-1 mRNA regulatory element. These were UCCAG/ACAA for YB-1 and a ∼50-nucleotide A-rich sequence for PABP that overlapped each other. PABP competes with YB-1 for binding to the YB-1 mRNA regulatory element and restores translational activity of YB-1 mRNA that has been inhibited by YB-1. Thus, YB-1 negatively regulates its own synthesis, presumably by specific interaction with the 3′UTR regulatory element, whereas PABP restores translational activity of YB-1 mRNA by displacing YB-1 from this element.

ACKNOWLEDGMENTS

We thank N. Sonenberg for providing pSP36T-LucA50 and pET3B PABP-His plasmids. We are grateful to T. Kuvshinkina and E. Serebrova for help in manuscript preparation.

This work was supported in part by the Russian Academy of Sciences (Programmes on “Molecular and Cellular Biology” and “Basic Sciences to Medicine”) and by a grant from the President of the Russian Federation (1959.2003.4).