Cellular Differentiation State Modulates the mRNA Export Activity of SR Proteins

J Cell Biol. 2017 Jul 3;216(7):1993-2009. doi: 10.1083/jcb.201610051. Epub 2017 Jun 7.

Abstract

SR proteins function in nuclear pre-mRNA processing, mRNA export, and translation. To investigate their cellular dynamics, we developed a quantitative assay, which detects differences in nucleocytoplasmic shuttling among seven canonical SR protein family members. As expected, SRSF2 and SRSF5 shuttle poorly in HeLa cells but surprisingly display considerable shuttling in pluripotent murine P19 cells. Combining individual-resolution cross-linking and immunoprecipitation (iCLIP) and mass spectrometry, we show that elevated arginine methylation of SRSF5 and lower phosphorylation levels of cobound SRSF2 enhance shuttling of SRSF5 in P19 cells by modulating protein-protein and protein-RNA interactions. Moreover, SRSF5 is bound to pluripotency-specific transcripts such as Lin28a and Pou5f1/Oct4 in the cytoplasm. SRSF5 depletion reduces and overexpression increases their cytoplasmic mRNA levels, suggesting that enhanced mRNA export by SRSF5 is required for the expression of pluripotency factors. Remarkably, neural differentiation of P19 cells leads to dramatically reduced SRSF5 shuttling. Our findings indicate that posttranslational modification of SR proteins underlies the regulation of their mRNA export activities and distinguishes pluripotent from differentiated cells.

Publication types

  • Comparative Study

MeSH terms

  • Active Transport, Cell Nucleus
  • Animals
  • Arginine
  • Cell Differentiation*
  • Cell Nucleus / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • HeLa Cells
  • Humans
  • Immunoprecipitation
  • Methylation
  • Mice
  • Neurogenesis
  • Phenotype
  • Phosphorylation
  • Pluripotent Stem Cells / metabolism*
  • Protein Binding
  • Protein Processing, Post-Translational
  • RNA Interference
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Serine-Arginine Splicing Factors / genetics
  • Serine-Arginine Splicing Factors / metabolism*
  • Tandem Mass Spectrometry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transfection

Substances

  • DNA-Binding Proteins
  • NFX1 protein, human
  • Nfx1 protein, mouse
  • RNA, Messenger
  • RNA-Binding Proteins
  • Repressor Proteins
  • SRSF2 protein, mouse
  • SRSF5 protein, human
  • SRSF5 protein, mouse
  • Transcription Factors
  • SRSF2 protein, human
  • Serine-Arginine Splicing Factors
  • Arginine