Identification of a human cDNA encoding a novel Bcl-x isoform

Biochem Biophys Res Commun. 1998 Jul 9;248(1):147-52. doi: 10.1006/bbrc.1998.8907.


Alternative splicing has been shown to generate two isoforms of the apoptosis regulator bcl-x, Bcl-xL and Bcl-xS, in humans. Here we describe the identification and characterization of a third splice variant of the human bcl-x gene. It differs from previously described bcl-x transcripts in two respects: (1) a novel facultative intron is spliced out at the 5' untranslated region and (2) the open reading frame arises from a continuous genomic sequence extending over the splice donor sites utilized by the bcl-xL and bcl-xS transcripts. Since the resulting molecule has an organisation homologous to mouse and rat Bcl-x beta we suggest calling this novel protein human Bcl-x beta. Northern blot analysis revealed that bcl-x beta mRNA is expressed in numerous cell lines. Like Bcl-xL, h-Bcl-x binds to the pro-apoptotic protein Bax, suggesting a functional activity in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Apoptosis
  • Base Sequence
  • Cell Line
  • Cloning, Molecular
  • DNA, Complementary
  • Humans
  • Introns
  • Molecular Sequence Data
  • Open Reading Frames
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / chemistry
  • Proto-Oncogene Proteins c-bcl-2 / genetics*
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • RNA Splicing
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • bcl-2-Associated X Protein
  • bcl-X Protein


  • BAX protein, human
  • BCL2L1 protein, human
  • DNA, Complementary
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • bcl-2-Associated X Protein
  • bcl-X Protein