SR proteins escort the U4/U6.U5 tri-snRNP to the spliceosome.


Journal Article

Pre-spliceosomes, formed in HeLa nuclear extracts and isolated by sedimentation on glycerol gradients, were chased into spliceosomes, the macromolecular enzyme that catalyzes intron removal. We demonstrate that the pre-spliceosome to spliceosome transition was dependent on ATP hydrolysis and required both a U-rich small nuclear ribonucleoprotein (U snRNP)-containing fraction and a fraction of non-snRNP factors. The active components in the non-snRNP fraction were identified as SR proteins and were purified to apparent homogeneity. Recombinant SR proteins (ASF, SC35, SRp55), as well as gel-purified SR proteins, with the exception of SRp20, were able to restore efficient spliceosome formation. We also demonstrate that the pre-spliceosome to spliceosome transition requires phosphorylated SR proteins. This is the first evidence that SR proteins are required for the pre-spliceosome to spliceosome transition, the step at which the U4/U6.U5 tri-snRNP assembles on the pre-mRNA. The results shown here, together with previous data, suggest U snRNPs require SR proteins as escorts to enter the assembling spliceosome.

Full Text

Duke Authors

Cited Authors

  • Roscigno, RF; Garcia-Blanco, MA

Published Date

  • September 1995

Published In

Volume / Issue

  • 1 / 7

Start / End Page

  • 692 - 706

PubMed ID

  • 7585254

Pubmed Central ID

  • 7585254

International Standard Serial Number (ISSN)

  • 1355-8382


  • eng

Conference Location

  • United States