Structural evidence for consecutive Hel308-like modules in the spliceosomal ATPase Brr2.

Department of Biochemistry and Molecular Genetics, University of Colorado Denver, Aurora, Colorado, USA.
Brr2 is a DExD/H-box helicase responsible for U4/U6 unwinding during spliceosomal activation. Brr2 contains two helicase-like domains, each of which is followed by a Sec63 domain with unknown function. We determined the crystal structure of the second Sec63 domain, which unexpectedly resembles domains 4 and 5 of DNA helicase Hel308. This, together with sequence similarities between Brr2's helicase-like domains and domains 1-3 of Hel308, led us to hypothesize that Brr2 contains two consecutive Hel308-like modules (Hel308-I and Hel308-II). Our structural model and mutagenesis data suggest that Brr2 shares a similar helicase mechanism with Hel308. We demonstrate that Hel308-II interacts with Prp8 and Snu114 in vitro and in vivo. We further find that the C-terminal region of Prp8 (Prp8-CTR) facilitates the binding of the Brr2-Prp8-CTR complex to U4/U6. Our results have important implications for the mechanism and regulation of Brr2's activity in splicing.
Mesh Terms:
Adenosine Triphosphatases, Animals, Humans, Molecular Sequence Data, Protein Structure, Secondary, Protein Structure, Tertiary, RNA Helicases, Ribonucleoprotein, U4-U6 Small Nuclear, Ribonucleoprotein, U5 Small Nuclear, Saccharomyces cerevisiae Proteins, Spliceosomes
Nat. Struct. Mol. Biol. Jul. 01, 2009; 16(7);731-9 [PUBMED:19525970]
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