Cell
Volume 74, Issue 4, 27 August 1993, Pages 597-608
Journal home page for Cell

Article
bcl-x, a bcl-2-related gene that functions as a dominant regulator of apoptotic cell death

https://doi.org/10.1016/0092-8674(93)90508-NGet rights and content

Abstract

We report the isolation of bcl-x, a bcl-2-related gene that can function as a bcl-2-independent regulator of programed cell death (apoptosis). Alternative splicing results in two distinct bcl-x mRNAs. The protein product of the larger mRNA, bcl-xL, is similar in size and predicted structure to Bcl-2. When stably transfected into an IL-3-dependent cell line, bcl-xL inhibits cell death upon growth factor withdrawal at least as well as bcl-2. Surprisingly, the second mRNA species, bcl-xS, encodes a protein that inhibits the ability of bcl-2 to enhance the survival of growth factor-deprived cells. In vivo, bcl-xS mRNA is expressed at high levels in cells that undergo a high rate of turnover, such as developing lymphocytes. In contrast, bcl-xL is found in tissues containing long-lived postmitotic cells, such as adult brain. Together these data suggest that bcl-x plays an important role in both positive and negative regulation of programed cell death.

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