Identification and purification of a 62,000-dalton protein that binds specifically to the polypyrimidine tract of introns. (original) (raw)

  1. M A García-Blanco,
  2. S F Jamison, and
  3. P A Sharp
  4. Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.

Abstract

A protein of molecular size 62,000 daltons (p62) was detected in HeLa cell nuclear extracts by UV cross-linking to mRNA precursors. p62 binds specifically to the polypyrimidine tract of the 3' splice site region of introns. p62 purified to homogeneity binds the polypyrimidine tract of pre-mRNAs. This binding does not require the AG dinucleotide at the 3' splice site. Alterations in the polypyrimidine tract that reduce the binding of p62 yield a corresponding reduction in the efficiency of formation of a U2 snRNP/pre-mRNA complex and splicing. The p62 protein is retained in the spliceosome, where it remains bound to the pre-mRNA. This polypyrimidine tract binding protein (pPTB) is proposed to be a critical component in recognition of the 3' splice site during splicing.

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