A conserved alpha-helical motif mediates the interaction of Sp1-like transcriptional repressors with the corepressor mSin3A.
Sp1-like proteins are defined by three highly homologous C(2)H(2) zinc finger motifs that bind GC-rich sequences found in the promoters of a large number of genes essential for mammalian cell homeostasis. Here we report that TIEG2, a transforming growth factor beta-inducible Sp1-like protein with antiproliferative functions, represses transcription through recruitment of the mSin3A-histone deacetylase complex. The interaction of TIEG2 with mSin3A is mediated by an alpha-helical repression motif (alpha-HRM) located within the repression domain (R1) of TIEG2. This alpha-HRM specifically associates with the second paired amphipathic helix (PAH2) domain of mSin3A. Mutations in the TIEG2 alpha-HRM domain that disrupt its helical structure abolish its ability to both bind mSin3A and repress transcription. Interestingly, the alpha-HRM is conserved in both the TIEG (TIEG1 and TIEG2) and BTEB (BTEB1, BTEB3, and BTEB4) subfamilies of Sp1-like proteins. The alpha-HRM from these proteins also mediates direct interaction with mSin3A and represses transcription. Surprisingly, we found that the alpha-HRM of the Sp1-like proteins characterized here exhibits structural and functional resemblance to the Sin3A-interacting domain previously described for the basic helix-loop-helix protein Mad1. Thus, our study defines a mechanism of transcriptional repression via the interactions of the alpha-HRM with the Sin3-histone deacetylase complex that is utilized by at least five Sp1-like transcriptional factors. More importantly, we demonstrate that a helical repression motif which mediates Sin3 interaction is not an exclusive structural and functional characteristic of the Mad1 subfamily but rather has a wider functional impact on transcriptional repression than previously demonstrated.
Zhang
J S
JS
Gastroenterology Research Unit, Mayo Clinic, Rochester, Minnesota 55901, USA.
Moncrieffe
M C
MC
Kaczynski
J
J
Ellenrieder
V
V
Prendergast
F G
FG
Urrutia
R
R
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D016466:CHO Cells; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism; D002455:Cell Division; D002942:Circular Dichroism; D006224:Cricetinae; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010452:Peptide Biosynthesis; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D056264:Sin3 Histone Deacetylase and Corepressor Complex; D016329:Sp1 Transcription Factor / Q000737:chemistry*; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000378:metabolism; D016335:Zinc Fingers
D051017:Apoptosis Regulatory Proteins; D018797:Cell Cycle Proteins; C115117:KLF11 protein, human; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C099683:SIN3A transcription factor; D016329:Sp1 Transcription Factor; D016212:Transforming Growth Factor beta; D008156:Luciferases; D005982:Glutathione Transferase; D056264:Sin3 Histone Deacetylase and Corepressor Complex