The Rel/NF-kappaB family directly activates expression of the apoptosis inhibitor Bcl-x(L)

Mol Cell Biol. 2000 Apr;20(8):2687-95. doi: 10.1128/MCB.20.8.2687-2695.2000.


The transcription factors of the Rel/NF-kappaB family are key regulators of immune and inflammatory responses and contribute to lymphocyte proliferation, survival, and oncogenesis. The absolute correlation between the antiapoptotic and oncogenic activities of the Rel/NF-kappaB oncoprotein v-Rel emphasizes the importance of characterizing the death antagonists under NF-kappaB control. Our recent finding that the prosurvival Bcl-2 homolog Bfl-1 (also called A1) is a direct transcriptional target of NF-kappaB raised the issue of whether NF-kappaB is a specific or global regulator of death antagonists in the Bcl-2 family. Here, we demonstrate that NF-kappaB differentially regulates the expression of particular Bcl-2-related death inhibitors and that it directly activates the expression of Bcl-x(L). While Bcl-x(L) was significantly upregulated by c-Rel and RelA, Bcl-2 was not. Importantly, stimuli that activate endogenous NF-kappaB factors also upregulated bcl-x gene expression and this effect was antagonized by an inhibitor of NF-kappaB activity. The expression of bcl-x suppressed apoptosis in the presence or absence of NF-kappaB activity. Functional analysis of the bcl-x promoter demonstrated that it is directly controlled by c-Rel. These results establish that NF-kappaB directly regulates the expression of distinct prosurvival factors in the Bcl-2 family, such as Bcl-x(L) and Bfl-1/A1. These findings raise the possibility that some of these factors may contribute to oncogenesis associated with aberrant Rel/NF-kappaB activity.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Apoptosis / genetics*
  • Cell Differentiation / genetics
  • Cell Division / genetics
  • Gene Expression Regulation*
  • HeLa Cells
  • Humans
  • NF-kappa B / genetics*
  • Proto-Oncogene Proteins c-bcl-2 / genetics*
  • bcl-X Protein


  • BCL2L1 protein, human
  • NF-kappa B
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-X Protein