Function of multiple Lis-Homology domain/WD-40 repeat-containing proteins in feed-forward transcriptional repression by silencing mediator for retinoic and thyroid receptor/nuclear receptor corepressor complexes.
Lis-homology (LisH) motifs are involved in protein dimerization, and the discovery of the conserved N-terminal LisH domain in transducin beta-like protein 1 and its receptor (TBL1 and TBLR1) led us to examine the role of this domain in transcriptional repression. Here we show that multiple beta-transducin (WD-40) repeat-containing proteins interact to form oligomers in solution and that oligomerization depends on the presence of the LisH domain in each protein. Repression of transcription, as assayed using Gal4 fusion proteins, also depended on the presence of the LisH domain, suggesting that oligomerization is a prerequisite for efficient transcriptional repression. Furthermore, we show that the LisH domain is responsible for the binding to the hypoacetylated histone H4 tail and for stable chromatin targeting by the nuclear receptor corepressor complex. Mutations in conserved residues in the LisH motif of TBL1 and TBLR1 block histone binding, oligomerization, and transcriptional repression, supporting the functional importance of the LisH motif in transcriptional repression. Our results indicate that another WD-40 protein, TBL3, also preferentially binds to the N-terminal domain of TBL1 and TBLR1, and forms oligomers with other WD-40 proteins. Finally, we observed that the WD-40 proteins RbAp46 and RbAp48 of the sin3A corepressor complex failed to dimerize. We also found the specific interaction UbcH/E2 with TBL1, but not RbAp46/48. Altogether, our results thus indicate that the presence of multiple LisH/WD-40 repeat containing proteins is exclusive to nuclear receptor corepressor/ silencing mediator for retinoic and thyroid receptor complexes compared with other class 1 histone deacetylase-containing corepessor complexes.
Choi
Hyo-Kyoung
HK
Department of Biochemistry and Molecular Biology, Center for Chronic Metabolic Disease Research, Yonsei University College of Medicine, Seoul 120-752, South Korea.
Choi
Kyung-Chul
KC
Kang
Hee-Bum
HB
Kim
Han-Cheon
HC
Lee
Yoo-Hyun
YH
Haam
Seungjoo
S
Park
Hyoung-Gi
HG
Yoon
Ho-Geun
HG
D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D004252:DNA Mutational Analysis; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056971:Nuclear Receptor Co-Repressor 1; D011485:Protein Binding; D018168:Receptors, Retinoic Acid / Q000235:genetics / Q000378:metabolism*; D011988:Receptors, Thyroid Hormone / Q000235:genetics / Q000378:metabolism*; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D002843:Chromatin; D006657:Histones; C539127:NCOR1 protein, human; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; D012097:Repressor Proteins