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Mol. Cell. Biol., 12 1996, 6810-6819, Vol 16, No. 12
SH Kim and RJ Lin
In addition to small nuclear RNAs and spliceosomal proteins, ATP hydrolysis
is needed for nuclear pre-mRNA splicing. A number of RNA- dependent ATPases
which are involved in several distinct ATP-dependent steps in splicing have
been identified in Saccharomyces cerevisiae and mammals. These so-called
DEAD/H ATPases contain conserved RNA helicase motifs, although RNA
unwinding activity has not been demonstrated in purified proteins. Here we
report the role of one such DEAH protein, PRP2 of S. cerevisiae, in
spliceosome activation. PRP2 bound to a precatalytic spliceosome prior to
the first step of splicing. By blocking the activity of a novel splicing
factor(s), HP, which was involved in a post-PRP2 step, we found that PRP2
hydrolyzed ATP to cause a change in the spliceosome without the occurrence
of splicing. The change was quite dramatic and could account for the
previously reported differences between the precatalytic,
pre-mRNA-containing spliceosome and the "active," intermediate-containing
spliceosome. The post-PRP2-ATP spliceosome was further isolated and could
carry out the subsequent reaction apparently in the absence of PRP2 and
ATP. We hypothesize that PRP2 functions as a molecular motor, similar to
some DExH ATPases in transcription, in the activation of the precatalytic
spliceosome for the transesterification reaction.
Copyright © 1996, American Society for Microbiology
Spliceosome activation by PRP2 ATPase prior to the first transesterification reaction of pre-mRNA splicing
Department of Molecular Biology, Beckman Research Institute of the City of Hope, Duarte, California 91010-3000, USA.
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