Research Article

Structure of a human catalytic step I spliceosome

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Science  04 Jan 2018:
eaar6401
DOI: 10.1126/science.aar6401

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Abstract

Splicing by the spliceosome involves branching and exon ligation. The branching reaction leads to the formation of the catalytic step I spliceosome (C complex). Here we report the cryo-EM structure of the human C complex at an average resolution of 4.1 Å. Compared to the structure of the S. cerevisiae C complex, the human complex contains 11 additional proteins. The step I splicing factors CCDC49 and CCDC94 (Cwc25 and Yju2 in S. cerevisiae, respectively) closely interact with the DEAH-family ATPase/helicase Prp16 and bridge the gap between Prp16 and the active site RNA elements. These features, together with structural comparison between the human C and C* complexes, reveal mechanistic insights into ribonucleoprotein remodeling and allow proposition of a working mechanism for the C-to-C* transition.

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