Affiliation:
1. Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, New York 14618
Abstract
ABSTRACT
Inactivation of poly(A) polymerase (encoded by
PAP1
) in
Saccharomyces cerevisiae
cells carrying the temperature-sensitive, lethal
pap1-1
mutation results in reduced levels of poly(A)
+
mRNAs. Genetic selection for suppressors of
pap1-1
yielded two recessive, cold-sensitive alleles of the gene
RRP6
. These suppressors,
rrp6-1
and
rrp6-2
, as well as a deletion of
RRP6
, allow growth of
pap1-1
strains at high temperature and partially restore the levels of poly(A)
+
mRNA in a manner distinct from the cytoplasmic mRNA turnover pathway and without slowing a rate-limiting step in mRNA decay. Subcellular localization of an Rrp6p-green fluorescent protein fusion shows that the enzyme residues in the nucleus. Phylogenetic analysis and the nature of the
rrp6-1
mutation suggest the existence of a highly conserved 3′-5′ exonuclease core domain within Rrp6p. As predicted, recombinant Rrp6p catalyzes the hydrolysis of a synthetic radiolabeled RNA in a manner consistent with a 3′-5′ exonucleolytic mechanism. Genetic and biochemical experiments indicate that Rrp6p interacts with poly(A) polymerase and with Npl3p, a poly(A)
+
mRNA binding protein implicated in pre-mRNA processing and mRNA nuclear export. These findings suggest that Rrp6p may interact with the mRNA polyadenylation system and thereby play a role in a nuclear pathway for the degradation of aberrantly processed precursor mRNAs.
Publisher
American Society for Microbiology
Subject
Cell Biology,Molecular Biology
Cited by
182 articles.
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