Hostname: page-component-7c8c6479df-ws8qp Total loading time: 0 Render date: 2024-03-28T11:09:53.102Z Has data issue: false hasContentIssue false

Dynamic conformational model for the role of ITS2 in pre-rRNA processing in yeast

Published online by Cambridge University Press:  20 August 2002

COLETTE A. CÔTÉ
Affiliation:
Genetics and Biochemistry Branch, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892-1766, USA
CHRIS L. GREER
Affiliation:
Department of Biological Chemistry, University of California, Irvine, Irvine, California 92697-1700, USA
BRENDA A. PECULIS
Affiliation:
Genetics and Biochemistry Branch, National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892-1766, USA
Get access

Abstract

Maturation of the large subunit rRNAs includes a series of cleavages that result in removal of the internal transcribed spacer (ITS2) that separates mature 5.8S and 25/28S rRNAs. Previous work demonstrated that formation of higher order secondary structure within the assembling pre-ribosomal particle is a prerequisite for accurate and efficient pre-rRNA processing. To date, it is not clear which specific sequences or secondary structures are required for processing. Two alternative secondary structure models exist for Saccharomyces cerevisiae ITS2. Chemical and enzymatic structure probing and phylogenetic comparisons resulted in one structure (Yeh & Lee, J Mol Biol, 1990, 211:699–712) referred to here as the “hairpin model.” More recently, an alternate folded structure was proposed (Joseph et al., Nucleic Acids Res, 1999, 27:4533–4540), called here the “ring model.” We have used a functional genetic assay to examine the potential significance of these predicted structures in processing. Our data indicate that elements of both structural models are important in efficient processing. Mutations that prevent formation of ring-specific structures completely blocked production of mature 25S rRNA, whereas those that primarily disrupt hairpin elements resulted in reduced levels of mature product. Based on these results, we propose a dynamic conformational model for the role of ITS2 in processing: Initial formation of the ring structure may be required for essential, early events in processing complex assembly and may be followed by an induced transition to the hairpin structure that facilitates subsequent processing events. In this model, yeast ITS2 elements may provide in cis certain of the functions proposed for vertebrate U8 snoRNA acting in trans.

Type
Research Article
Copyright
© 2002 RNA Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)