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Journal Article

Structural basis for functional cooperation between tandem helicase cassettes in Brr2-mediated remodeling of the spliceosome.

MPS-Authors
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Mozaffari-Jovin,  S.
Department of Cellular Biochemistry, MPI for biophysical chemistry, Max Planck Society;

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Pena,  V.
Research Group of Macromolecular Crystallography, MPI for Biophysical Chemistry, Max Planck Society;

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Lührmann,  R.
Department of Cellular Biochemistry, MPI for biophysical chemistry, Max Planck Society;

Fulltext (public)

1564003.pdf
(Publisher version), 2MB

Supplementary Material (public)

1564003-Suppl.pdf
(Supplementary material), 5MB

Citation

Santos, K. F., Mozaffari-Jovin, S., Weber, G., Pena, V., Lührmann, R., & Wahl, M. C. (2012). Structural basis for functional cooperation between tandem helicase cassettes in Brr2-mediated remodeling of the spliceosome. Proceedings of the National Academy of Sciences of the United States of America, 109(43), 17418-17423. doi:10.1073/pnas.1208098109.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0010-19EC-C
Abstract
Assembly of a spliceosome, catalyzing precursor–messenger RNA splicing, involves multiple RNA–protein remodeling steps, driven by eight conserved DEXD/H-box RNA helicases. The 250-kDa Brr2 enzyme, which is essential for U4/U6 di-small nuclear ribonucleoprotein disruption during spliceosome catalytic activation and for spliceosome disassembly, is the only member of this group that is permanently associated with the spliceosome, thus requiring its faithful regulation. At the same time, Brr2 represents a unique subclass of superfamily 2 nucleic acid helicases, containing tandem helicase cassettes. Presently, the mechanistic and regulatory consequences of this unconventional architecture are unknown. Here we show that in human Brr2, two ring-like helicase cassettes intimately interact and functionally cooperate and how retinitis pigmentosa-linked Brr2 mutations interfere with the enzyme’s function. Only the N-terminal cassette harbors ATPase and helicase activities in isolation. Comparison with other helicases and mutational analyses show how it threads single-stranded RNA, and structural features suggest how it can load onto an internal region of U4/U6 di-snRNA. Although the C-terminal cassette does not seem to engage RNA in the same fashion, it binds ATP and strongly stimulates the N-terminal helicase. Mutations at the cassette interface, in an intercassette linker or in the C-terminal ATP pocket, affect this cross-talk in diverse ways. Together, our results reveal the structural and functional interplay between two helicase cassettes in a tandem superfamily 2 enzyme and point to several sites through which Brr2 activity may be regulated.