Two modes of transcriptional activation at native promoters by NF-kappaB p65

PLoS Biol. 2009 Mar 31;7(3):e73. doi: 10.1371/journal.pbio.1000073.

Abstract

The NF-kappaB family of transcription factors is crucial for the expression of multiple genes involved in cell survival, proliferation, differentiation, and inflammation. The molecular basis by which NF-kappaB activates endogenous promoters is largely unknown, but it seems likely that it should include the means to tailor transcriptional output to match the wide functional range of its target genes. To dissect NF-kappaB-driven transcription at native promoters, we disrupted the interaction between NF-kappaB p65 and the Mediator complex. We found that expression of many endogenous NF-kappaB target genes depends on direct contact between p65 and Mediator, and that this occurs through the Trap-80 subunit and the TA1 and TA2 regions of p65. Unexpectedly, however, a subset of p65-dependent genes are transcribed normally even when the interaction of p65 with Mediator is abolished. Moreover, a mutant form of p65 lacking all transcription activation domains previously identified in vitro can still activate such promoters in vivo. We found that without p65, native NF-kappaB target promoters cannot be bound by secondary transcription factors. Artificial recruitment of a secondary transcription factor was able to restore transcription of an otherwise NF-kappaB-dependent target gene in the absence of p65, showing that the control of promoter occupancy constitutes a second, independent mode of transcriptional activation by p65. This mode enables a subset of promoters to utilize a wide choice of transcription factors, with the potential to regulate their expression accordingly, whilst remaining dependent for their activation on NF-kappaB.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3T3 Cells
  • Animals
  • Cell Line
  • DNA-Binding Proteins / metabolism
  • Gene Expression Regulation*
  • Humans
  • Mediator Complex
  • Mice
  • Oligonucleotide Array Sequence Analysis
  • Promoter Regions, Genetic*
  • Proteins / genetics
  • Proteins / metabolism*
  • Transcription Factor RelA / genetics
  • Transcription Factor RelA / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcriptional Activation*
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • DNA-Binding Proteins
  • Med17 protein, human
  • Mediator Complex
  • Proteins
  • Transcription Factor RelA
  • Transcription Factors
  • Tumor Necrosis Factor-alpha