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MOLECULAR AND CELLULAR BIOLOGY, Mar. 1994, p. 1689-1697 Vol. 14, No. 3 0270-7306/94/$04.00+(
 

Summary: MOLECULAR AND CELLULAR BIOLOGY, Mar. 1994, p. 1689-1697 Vol. 14, No. 3
0270-7306/94/$04.00+(
Copyright C) 1994, American Society for Microbiology
Mutations in an Essential U2 Small Nuclear RNA Structure
Cause Cold-Sensitive U2 Small Nuclear Ribonucleoprotein
Function by Favoring Competing Alternative U2
RNA Structures
MARY I. ZAVANELLI, JESSICA S. BRITTON, A. HALLER IGEL, AND MANUEL ARES, JR.*
Biology Department, Sinisheimer Laboratories, University of California, Santa Cruz, Santa Cruz, California 95064
Received 1 October 1993/Returned for modification 30 November 1993/Accepted 13 December 1993
Mutations in stem-loop Ila ofyeast U2 RNA cause cold-sensitive growth and cold-sensitive U2 small nuclear
ribonucleoprotein function in vitro. Cold-sensitive U2 small nuclear RNA adopts an alternative conformation
that occludes the loop and disrupts the stem but does so at both restrictive and permissive temperatures. To
determine whether alternative U2 RNA structure causes the defects, we tested second-site mutations in U2
predicted to disrupt the alternative conformation. We find that such mutations efficiently suppress the
cold-sensitive phenotypes and partially restore correct U2 RNA folding. A genetic search for additional
suppressors of cold sensitivity revealed two unexpected mutations in the base of an adjacent stem-loop. Direct
probing of RNA structure in vivo indicates that the suppressors of cold sensitivity act to improve the stability
of the essential stem relative to competing alternative structures by disrupting the alternative structures. We
suggest that many of the numerous cold-sensitive mutations in a variety of RNAs and RNA-binding proteins

  

Source: Ares Jr., Manny - Department of Molecular, Cell, and Developmental Biology, University of California at Santa Cruz

 

Collections: Biology and Medicine