A dual role for BBP/ScSF1 in nuclear pre-mRNA retention and splicing

EMBO J. 2000 Apr 17;19(8):1873-86. doi: 10.1093/emboj/19.8.1873.


The MSL5 gene, which codes for the splicing factor BBP/ScSF1, is essential in Saccharomyces cerevisiae, yet previous analyses failed to reveal a defect in assembly of (pre)-spliceosomes or in vitro splicing associated with its depletion. We generated 11 temperature-sensitive (ts) mutants and one cold-sensitive (cs) mutant in the corresponding gene and analyzed their phenotypes. While all mutants were blocked in the formation of commitment complex 2 (CC2) at non-permissive and permissive temperature, the ts mutants showed no defect in spliceosome formation and splicing in vitro. The cs mutant was defective in (pre)-spliceosome formation, but residual splicing activity could be detected. In vivo splicing of reporters carrying introns weakened by mutations in the 5' splice site and/or in the branchpoint region was affected in all mutants. Pre-mRNA leakage to the cytoplasm was strongly increased (up to 40-fold) in the mutants. A combination of ts mutants with a disruption of upf1, a gene involved in nonsense-mediated decay, resulted in a specific synthetic growth phenotype, suggesting that the essential function of SF1 in yeast could be related to the retention of pre-mRNA in the nucleus.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Amino Acid Sequence
  • DNA-Binding Proteins*
  • Molecular Sequence Data
  • Mutagenesis
  • Phenotype
  • Plasmids
  • Protein Structure, Tertiary
  • RNA Precursors / metabolism*
  • RNA Splicing Factors
  • RNA Splicing*
  • RNA, Messenger / metabolism*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / physiology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Amino Acid
  • Spliceosomes / metabolism*
  • Temperature
  • Transcription Factors*


  • DNA-Binding Proteins
  • MSL5 protein, S cerevisiae
  • RNA Precursors
  • RNA Splicing Factors
  • RNA, Messenger
  • RNA-Binding Proteins
  • SF1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Adenosine Triphosphate