The LIM-homeodomain transcription factor LMX1B regulates expression of NF-kappa B target genes.
LMX1B is a LIM-homeodomain transcription factor essential for development. Putative LMX1B target genes have been identified through mouse gene targeting studies, but their identity as direct LMX1B targets remains hypothetical. We describe here the first molecular characterization of LMX1B target gene regulation. Microarray analysis using a tetracycline-inducible LMX1B expression system in HeLa cells revealed that a subset of NF-kappaB target genes, including IL-6 and IL-8, are upregulated in LMX1B-expressing cells. Inhibition of NF-kappaB activity by short interfering RNA-mediated knock-down of p65 impairs, while activation of NF-kappaB activity by TNF-alpha synergizes induction of NF-kappaB target genes by LMX1B. Chromatin immunoprecipitation demonstrated that LMX1B binds to the proximal promoter of IL-6 and IL-8 in vivo, in the vicinity of the characterized kappaB site, and that LMX1B recruitment correlates with increased NF-kappaB DNA association. IL-6 promoter-reporter assays showed that the kappaB site and an adjacent putative LMX1B binding motif are both involved in LMX1B-mediated transcription. Expression of NF-kappaB target genes is affected in the kidney of Lmx1b(-/-) knock-out mice, thus supporting the biological relevance of our findings. Together, these data demonstrate for the first time that LMX1B directly regulates transcription of a subset of NF-kappaB target genes in cooperation with nuclear p50/p65 NF-kappaB.
Rascle
Anne
A
Institute for Molecular and Cellular Anatomy, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany. anne.rascle@vkl.uni-regensburg.de
Neumann
Tanja
T
Raschta
Anne-Sarah
AS
Neumann
Astrid
A
Heining
Eva
E
Kastner
Juergen
J
Witzgall
Ralph
R
D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D005786:Gene Expression Regulation; D006367:HeLa Cells; D018398:Homeodomain Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D016899:Interferon-beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000235:genetics; D016209:Interleukin-8 / Q000235:genetics; D007668:Kidney / Q000378:metabolism; D060850:LIM-Homeodomain Proteins; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D034421:Sus scrofa; D051996:Transcription Factor RelA / Q000378:metabolism; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D015533:Transcriptional Activation / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D018398:Homeodomain Proteins; D015850:Interleukin-6; D016209:Interleukin-8; C112149:LIM homeobox transcription factor 1 beta; D060850:LIM-Homeodomain Proteins; D016328:NF-kappa B; D051996:Transcription Factor RelA; D014157:Transcription Factors; D016899:Interferon-beta