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Conservation of structure and subunit interactions in yeast homologues of
 

Summary: Conservation of structure and subunit
interactions in yeast homologues of
splicing factor 3b (SF3b) subunits
HALLER IGEL, SANDRA WELLS, RHONDA PERRIMAN, and MANUEL ARES, JR.
Center for the Molecular Biology of RNA, Biology Department, Sinsheimer Laboratories,
University of California at Santa Cruz, Santa Cruz, California 95064, USA
ABSTRACT
Human SAP 49, a subunit of the multimeric splicing factor 3b (SF3b), contains two RNA recognition motifs (RRMs) and
binds another SF3b subunit called SAP 145, whose yeast homologue is CUS1. Here we show that the predicted yeast
open reading frame YOR319w (HSH49) encodes an essential yeast splicing factor. Using bacterially expressed pro-
teins, we find that yeast HSH49 binds CUS1. Mutations that alter putative RNA-binding residues of either HSH49 RRM
are lethal in vivo, but do not prevent binding to CUS1 in vitro, suggesting that the predicted RNA-binding surfaces of
HSH49 are not required for interaction with CUS1. In vivo interaction tests show that HSH49 and CUS1 associate
primarily through the N-terminal RRM of HSH49. Recombinant HSH49 protein has a general RNA-binding activity that
does not require CUS1. The parallels in structure and interaction between two SF3b subunits from yeast implies that
the mechanism of SF3b action is highly conserved.
Keywords: RNA-binding proteins; RNA processing; Saccharomyces cerevisiae; SAP 49
INTRODUCTION
Removal of introns from nuclear primary transcripts
(pre-mRNA) occurs in the spliceosome, a fluid assem-

  

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

 

Collections: Biology and Medicine