SR protein family members display diverse activities in the formation of nascent and mature mRNPs in vivo

Mol Cell. 2009 Apr 24;34(2):179-90. doi: 10.1016/j.molcel.2009.02.031.


The SR proteins are a family of pre-mRNA splicing factors with additional roles in gene regulation. To investigate individual family members in vivo, we generated a comprehensive panel of stable cell lines expressing GFP-tagged SR proteins under endogenous promoter control. Recruitment of SR proteins to nascent FOS RNA was transcription dependent and RNase sensitive, with unique patterns of accumulation along the gene specified by the RNA recognition motifs (RRMs). In addition, all SR protein interactions with Pol II were RNA dependent, indicating that SR proteins are not preassembled with Pol II. SR protein interactions with RNA were confirmed in situ by FRET/FLIM. Interestingly, SC35-GFP also exhibited FRET with DNA and failed to associate with cytoplasmic mRNAs, whereas all other SR proteins underwent nucleocytoplasmic shuttling and associated with specific nuclear and cytoplasmic mRNAs. Because different constellations of SR proteins bound nascent, nuclear, and cytoplasmic mRNAs, mRNP remodeling must occur throughout an mRNA's lifetime.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatin Immunoprecipitation
  • Chromosomes, Artificial, Bacterial / genetics
  • Fluorescence Resonance Energy Transfer
  • Genes, fos
  • Green Fluorescent Proteins / analysis
  • HeLa Cells
  • Humans
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Nuclear Proteins / physiology*
  • Promoter Regions, Genetic
  • RNA Splicing / physiology*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • RNA-Binding Proteins / physiology*
  • Recombinant Fusion Proteins / analysis
  • Ribonucleoproteins / biosynthesis*
  • Ribonucleoproteins / metabolism
  • Transcription, Genetic


  • Nuclear Proteins
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • Ribonucleoproteins
  • messenger ribonucleoprotein
  • Green Fluorescent Proteins