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

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