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Bms1p, a novel GTP-binding protein, and the related Tsr1p are required for distinct steps of 40S ribosome biogenesis in yeast

Published online by Cambridge University Press:  25 September 2001

DANIEL GELPERIN
Affiliation:
Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA Current address: Department of Cellular and Developmental Biology, Yale University, New Haven, CT 06520-8103.
LYNN HORTON
Affiliation:
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
JAKE BECKMAN
Affiliation:
Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
JACK HENSOLD
Affiliation:
Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA Department of Medicine, Cleveland Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
SANDRA K. LEMMON
Affiliation:
Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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Abstract

Bms1p and Tsr1p define a novel family of proteins required for synthesis of 40S ribosomal subunits in Saccharomyces cerevisiae. Both are essential and localize to the nucleolus. Tsr1p shares two extended regions of similarity with Bms1p, but the two proteins function at different steps in 40S ribosome maturation. Inactivation of Bms1p blocks at an early step, leading to disappearance of 20S and 18S rRNA precursors. Also, slight accumulation of an aberrant 23S product and significant 35S accumulation are observed, indicating that pre-rRNA processing at sites A0, A1, and A2 is inhibited. In contrast, depletion of Tsr1p results in accumulation of 20S rRNA. Because processing of 20S to 18S rRNA occurs in the cytoplasm, this suggests that Tsr1p is required for assembly of a transport- or maturation-competent particle or is specifically required for transport of 43S pre-ribosomal particles, but not 60S ribosome precursors, from the nucleus to the cytosol. Finally, Bms1p is a GTP-binding protein, the first found to function in ribosome assembly or rRNA processing.

Type
Research Article
Information
RNA , Volume 7 , Issue 9 , September 2001 , pp. 1268 - 1283
Copyright
2001 RNA Society

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