The Major Cytoplasmic mRNP Protein, p50, Is Required for Efficient mRNA Translation in vitro

E. A. Kovrigina,¹ D. V. Nashchekin,¹ V. M. Evdokimova,¹ and L. P. Ovchinnikov^1,2

¹Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (7-095) 924-04-93; E-mail: ovchinn@sun.ipr.serpukhov.su

²To whom correspondence should be addressed.

Submitted July 12, 1996; revision submitted August 20, 1996.

The major cytoplasmic mRNP protein of somatic cells, p50, belongs to the Y-box binding transcription factor family and can control gene expression at two levels: at the level of mRNA transcription and at the level of its translation. Earlier it was established that p50 is responsible for the inactive state of the mRNA within free mRNPs. In this work we show that the Y-box containing DNA (Y-DNA), binding mainly to p50 in rabbit reticulocyte lysates, causes translation inhibition of the endogenous and exogenous globin mRNA as well as the prokaryotic beta-galactosidase mRNA. Pre-incubation of the Y-DNA with purified p50 prevents inhibition. Inhibition of protein biosynthesis by the Y-DNA is not due to degradation or functional mRNA inactivation. The inhibition is accompanied by polyribosome decay and dissociation of a newly synthesized protein from the ribosomes. The results indicate that the inhibition of protein biosynthesis by Y-DNA occurs mainly at the initiation stage and that p50 is an essential component of the translation initiation apparatus.

KEY WORDS: mRNP, p50, translation regulation, transcription factors, Y-box.

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