Recruitment of SMRT/N-CoR-mSin3A-HDAC-repressing complexes is not a general mechanism for BTB/POZ transcriptional repressors: the case of HIC-1 and gammaFBP-B.
Hypermethylated in cancer (HIC-1), a new candidate tumor suppressor gene located in 17p13.3, encodes a protein with five C(2)H(2) zinc fingers and an N-terminal broad complex, tramtrack, and bric a brac/poxviruses and zinc-finger (BTB/POZ) domain found in actin binding proteins or transcriptional regulators involved in chromatin modeling. In the human ... B cell lymphoma (BCL-6) and promyelocityc leukemia (PLZF) oncoproteins, this domain mediates transcriptional repression through its ability to recruit a silencing mediator of retinoid and thyroid hormone receptor (SMRT)/nuclear receptor corepressor (N-CoR)-mSin3A-histone deacetylase (HDAC) complex, a mechanism shared with numerous transcription factors. HIC-1 appears unique because it contains a 13-aa insertion acquired late in evolution, because it is not found in its avian homologue, gammaF1-binding protein isoform B (gammaFBP-B), a transcriptional repressor of the gammaF-crystallin gene. This insertion, located in a conserved region involved in the dimerization and scaffolding of the BTB/POZ domain, mainly affects slightly the ability of the HIC-1 and gammaFBP-B BTB/POZ domains to homo- and heterodimerize in vivo, as shown by mammalian two-hybrid experiments. Both the HIC-1 and gammaFBP-B BTB/POZ domains behave as autonomous transcriptional repression domains. However, in striking contrast with BCL-6 and PLZF, both HIC-1 and gammaFBP-B similarly fail to interact with members of the HDAC complexes (SMRT/N-CoR, mSin3A or HDAC-1) in vivo and in vitro. In addition, a general and specific inhibitor of HDACs, trichostatin A, did not alleviate the HIC-1- and gammaFBP-B-mediated transcriptional repression, as previously shown for BCL-6. Taken together, our studies show that the recruitment onto target promoters of an HDAC complex is not a general property of transcriptional repressors containing a conserved BTB/POZ domain.
Mesh Terms:
Animals, Butyrates, DNA-Binding Proteins, Gene Silencing, Genes, Tumor Suppressor, Histone Deacetylase Inhibitors, Histone Deacetylases, Humans, Hydroxamic Acids, Kruppel-Like Transcription Factors, Nuclear Proteins, Nuclear Receptor Co-Repressor 1, Nuclear Receptor Co-Repressor 2, Protein Binding, Protein Structure, Tertiary, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-bcl-6, Rabbits, Repressor Proteins, Transcription Factors, Two-Hybrid System Techniques
Animals, Butyrates, DNA-Binding Proteins, Gene Silencing, Genes, Tumor Suppressor, Histone Deacetylase Inhibitors, Histone Deacetylases, Humans, Hydroxamic Acids, Kruppel-Like Transcription Factors, Nuclear Proteins, Nuclear Receptor Co-Repressor 1, Nuclear Receptor Co-Repressor 2, Protein Binding, Protein Structure, Tertiary, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-bcl-6, Rabbits, Repressor Proteins, Transcription Factors, Two-Hybrid System Techniques
Proc. Natl. Acad. Sci. U.S.A.
Date: Dec. 21, 1999
PubMed ID: 10611298
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