Corecruitment of the Grg4 repressor by PU.1 is critical for Pax5-mediated repression of B-cell-specific genes.
PU.1 and Pax5 are important regulators of immunoglobulin heavy-chain (IgH) gene expression in B lineage cells. We have previously shown that PU.1 can potentiate the transcription of an IgH HS1,2 enhancer-linked reporter gene, and that Pax5 represses the same enhancer in transient transfection assays. Here we report that PU.1, like Pax5, can recruit and physically interact with a member of the Groucho family of co-repressors, Grg4. As a consequence, PU.1 in conjunction with Pax5 represses enhancer function in a position-dependent manner when Grg4 is recruited. Interestingly, Grg4 levels decrease following B-cell activation, suggesting temporal regulation of Grg4. Moreover, the joining-chain promoter, with an activity pattern and architecture resembling HS1,2 can also be repressed by the combinatorial action of Pax5/PU.1/Grg4. These data indicate that Pax5 depends on PU.1, acting in cis, for stable recruitment of Grg co-repressors to B-cell-specific genes.
Microbiology and Tumorbiology Center, Karolinska Institutet, Stockholm Sweden.
Ylva
Y
Linderson
Dirk
D
Eberhard
Stephen
S
Malin
Annica
A
Johansson
Meinrad
M
Busslinger
Sven
S
Pettersson
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D001483:Base Sequence; D019556:COS Cells; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D005803:Genes, Immunoglobulin / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics; D005914:Globins / Q000235:genetics; D006801:Humans; D007144:Immunoglobulin J-Chains / Q000235:genetics; D008156:Luciferases / Q000032:analysis; D008213:Lymphocyte Activation; D051379:Mice; D008969:Molecular Sequence Data; D051757:PAX5 Transcription Factor; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D000099232:Proto-Oncogene Protein Spi-1
D004268:DNA-Binding Proteins; D005914:Globins; D007144:Immunoglobulin J-Chains; D008156:Luciferases; D051757:PAX5 Transcription Factor; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D000099232:Proto-Oncogene Protein Spi-1; C497281:PAX5 protein, human; C497282:Pax5 protein, mouse