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

Robert F. Roscigno, Mariano Garcia-Blanco

Research output: Contribution to journalArticle

126 Citations (Scopus)

Abstract

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-spllceosome 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.

Original languageEnglish (US)
Pages (from-to)692-706
Number of pages15
JournalRNA
Volume1
Issue number7
StatePublished - 1995
Externally publishedYes

Fingerprint

Small Nuclear Ribonucleoproteins
Spliceosomes
Proteins
RNA Precursors
Recombinant Proteins
Glycerol
Introns
Hydrolysis
Adenosine Triphosphate
Gels

Keywords

  • Commitment complex
  • pre-mRNA splicing
  • Pre-spliceosome

ASJC Scopus subject areas

  • Genetics
  • Molecular Biology

Cite this

SR proteins escort the U4/U6·U5 tri-snRNP to the spliceosome. / Roscigno, Robert F.; Garcia-Blanco, Mariano.

In: RNA, Vol. 1, No. 7, 1995, p. 692-706.

Research output: Contribution to journalArticle

Roscigno, Robert F. ; Garcia-Blanco, Mariano. / SR proteins escort the U4/U6·U5 tri-snRNP to the spliceosome. In: RNA. 1995 ; Vol. 1, No. 7. pp. 692-706.
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N2 - 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-spllceosome 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.

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