Mini-REVIEW: Ribosomal RNAs in Translation Termination: Facts and Hypotheses

A. L. Arkov and E. J. Murgola^*

Department of Molecular Genetics (Box 11), The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA; fax: (713) 794-4295; E-mail: ejm@mdacc.tmc.edu

^* To whom correspondence should be addressed.

Received June 2, 1999

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It is now well established that ribosomal RNAs (rRNAs) play an active role in every aspect of translation. This review focuses on recent evidence for the involvement of rRNAs from both subunits of the ribosome in translation termination. This evidence comprises data obtained with rRNA mutants both in vivo and in vitro. In particular, mutations in specific regions of rRNAs caused readthrough of nonsense codons in vivo. Consistent with their in vivo characteristics, the mutations decreased the productive association of the ribosome with release factor 2 (RF2) and the efficiency of catalysis of peptidyl-tRNA hydrolysis in the presence of RF2 in realistic in vitro termination systems. It is now evident that genetic selections for termination-defective mutants in vivo and their characterization in realistic in vitro termination assays will rapidly advance our understanding of the mechanism of termination.

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KEY WORDS: termination, ribosomal RNA, release factor, helix 34, helix 44, GTPase center, peptidyl transferase, Escherichia coli

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