Open AccessHuman T-Cell Lymphotropic Virus Type 1 Tax Represses c-Myb-Dependent Transcription through Activation of the NF-κB Pathway and Modulation of Coactivator Usage
Author(s) -
Christophe Nicot,
Renaud Mahieux,
Cynthia A. Pise-Masison,
John Brady,
Antoine Gessain,
Yasuhiro Shoji,
Genoveffa Franchini
Publication year - 2001
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.21.21.7391-7402.2001
Subject(s) - biology , transcription factor , coactivator , psychological repression , myb , transcription (linguistics) , signal transduction , nf κb , microbiology and biotechnology , p300 cbp transcription factors , activating transcription factor 2 , cancer research , promoter , gene expression , genetics , gene , linguistics , philosophy , histone acetyltransferases
The proto-oncogene c-myb is essential for a controlled balance between cell growth and differentiation. Aberrant c-Myb activity has been reported for numerous human cancers, and enforced c-Myb transcription can transform cells of lymphoid origin by stimulating cellular proliferation and inhibiting apoptotic pathways. Here we demonstrate that activation of the NF-kappaB pathway by the HTLV-1 Tax protein leads to transcriptional inactivation of c-Myb. This conclusion was supported by the fact that Tax mutants unable to stimulate the NF-kappaB pathway could not inhibit c-Myb transactivating functions. In addition, inhibition of Tax-mediated NF-kappaB activation by coexpression of IkappaBalpha restored c-Myb transcription, and Tax was unable to block c-Myb transcription in a NEMO knockout cell line. Importantly, physiological stimuli, such as signaling with the cellular cytokines tumor necrosis factor alpha, interleukin 1 beta (IL-1beta), and lipopolysaccharide, also inhibited c-Myb transcription. These results uncover a new link between extracellular signaling and c-Myb-dependent transcription. The mechanism underlying NF-kappaB-mediated repression was identified as sequestration of the coactivators CBP/p300 by RelA. Interestingly, an amino-terminal deletion form of p300 lacking the C/H1 and KIX domains and unable to bind RelA retained the ability to stimulate c-Myb transcription and prevented NF-kappaB-mediated repression.