The Major Core Protein of Messenger Ribonucleoprotein Particles (p50) Promotes Initiation of Protein Biosynthesis in Vitro*
- Valentina M. Evdokimova‡,
- Elizaveta A. Kovrigina‡,
- Dmitry V. Nashchekin‡,
- Elena K. Davydova‡,
- John W. B. Hershey§ and
- Lev P. Ovchinnikov‡¶
- From the ‡Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region 142292, Russian Federation and the §Department of Biological Chemistry, School of Medicine, University of California, Davis, California 95616
Abstract
The major core protein of cytoplasmic messenger ribonucleoprotein particles (p50) has been shown previously to inhibit protein synthesis in vitro and in vivo. Furthermore, p50 is highly homologous to the Y-box-binding transcription factor family of proteins, binds DNA containing the Y-box motif, and thus may have a dual function in cells as a regulator of both transcription and translation. Here we show that binding or removal of p50 from rabbit reticulocyte lysate by monospecific antibodies to p50 strongly inhibits translation of endogenous and exogenous globin mRNAs as well as prokaryotic β-galactosidase mRNA in a rabbit reticulocyte cell-free system. Thus, depending on the conditions, p50 not only may act as a translational repressor, but may also be required for protein synthesis. Translation inhibition with anti-p50 antibodies is not a result of mRNA degradation or its functional inactivation. The inhibition does not change the ribosome transit time, and therefore, it does not affect elongation/termination of polypeptide chains. The inhibition with anti-p50 antibodies is followed by a decay of polysomes and accumulation of the 48 S preinitiation complex. These results suggest that p50 participates in initiation of protein biosynthesis. Although uninvolved in the formation of the 48 S preinitiation complex, p50 is necessary either for attachment of the 60 S ribosomal subunit or for previous 5′-untranslated region scanning by the 43 S preinitiation complex.
Footnotes
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↵* This work was supported by Grants N 93-04-06548 and N 96-04-48903 from the Russian Basic Research Foundation, Grant MCB-91-23549 from the National Science Foundation, Grant N MUCOOO from the International Science Foundation, and Grant RBI-282 from the United States Civilian Research and Development Foundation.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed. Tel./Fax: 95-924-0493; E-mail: ovchinn{at}sun.ipr.serpukhov.su.
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↵1 The abbreviations used are: mRNPs, messenger ribonucleoprotein particles; PAGE, polyacrylamide gel electrophoresis; FRG Y2, frog Y-box transcription factor 2.
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↵2 V. A. Ustinov, M. A. Skabkin, V. M. Evdokimova, J. W. B. Hershey, and L. P. Ovchinnikov, manuscript in preparation.
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- Received March 17, 1997.
- Revision received November 13, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
