Regulation of BCL-X splicing reveals a role for the polypyrimidine tract binding protein (PTBP1/hnRNP I) in alternative 5' splice site selection

Pamela Bielli, Matteo Bordi, Valentina Di Biasio, Claudio Sette

Research output: Contribution to journalArticle

Abstract

Alternative splicing (AS) modulates many physiological and pathological processes. For instance, AS of the BCL-X gene balances cell survival and apoptosis in development and cancer. Herein, we identified the polypyrimidine tract binding protein (PTBP1) as a direct regulator of BCL-X AS. Overexpression of PTBP1 promotes selection of the distal 5' splice site in BCL-X exon 2, generating the pro-apoptotic BCLXs splice variant. Conversely, depletion of PTBP1 enhanced splicing of the anti-apoptotic BCL-XL variant. In vivo cross-linking experiments and site-directed mutagenesis restricted the PTBP1 binding site to a polypyrimidine tract located between the two alternative 5' splice sites. Binding of PTBP1 to this site was required for its effect on splicing. Notably, a similar function of PTBP1 in the selection of alternative 5' splice sites was confirmed using the USP5 gene as additional model. Mechanistically, PTBP1 displaces SRSF1 binding from the proximal 5' splice site, thus repressing its selection. Our study provides a novel mechanism of alternative 5' splice site selection by PTBP1 and indicates that the presence of a PTBP1 binding site between two alternative 5' splice sites promotes selection of the distal one, while repressing the proximal site by competing for binding of a positive regulator.

Original languageEnglish
Pages (from-to)12070-12081
Number of pages12
JournalNucleic Acids Research
Volume42
Issue number19
DOIs
Publication statusPublished - Oct 29 2014

ASJC Scopus subject areas

  • Genetics
  • Medicine(all)

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