Structural basis for m3G-cap-mediated nuclear import of spliceosomal UsnRNPs by snurportin1.

ABSTRACT: In higher eukaryotes the biogenesis of spliceosomal UsnRNPs involves a nucleocytoplasmic shuttling cycle. After the m7G-cap-dependent export of the snRNAs U1, U2, U4 and U5 to the cytoplasm, each of these snRNAs associates with seven Sm proteins. Subsequently, the m7G-cap is hypermethylated to the 2,2,7-trimethylguanosine (m3G)-cap. The import adaptor snurportin1 recognises the m3G-cap and facilitates the nuclear import of the UsnRNPs by binding to importin-beta. Here we report the crystal structure of the m3G-cap-binding domain of snurportin1 with bound m3GpppG at 2.4 A resolution, revealing a structural similarity to the mRNA-guanyly-transferase. Snurportin1 binds both the hypermethylated cap and the first nucleotide of the RNA in a stacked conformation. This binding mode differs signifi

SUBMITTER: Strasser A 

PROVIDER: S-EPMC1173142 | biostudies-literature | 2005 Jul

REPOSITORIES: biostudies-literature