CtBP contributes quantitatively to Knirps repression activity in an NAD binding-dependent manner.
Transcriptional repressors often employ multiple activities, but the molecular mechanisms and physiological relevance of this functional diversity remain obscure. The Drosophila melanogaster Knirps repressor uses CtBP corepressor-dependent and -independent pathways. To separately analyze the components of Knirps repression activity, we elucidated the specific repression properties of CtBP and of Knirps subdomains. Like Knirps, CtBP represses adjacent transcriptional activators; but unlike Knirps, CtBP is unable to repress basal promoter elements. We determined that the ability of CtBP to recapitulate only a subset of Knirps activities is due to a quantitative, rather than qualitative, deficiency in repression activity. The CtBP-dependent portion of Knirps synergizes with the CtBP-independent repression activity to potently repress promoter elements from enhancer- or promoter-proximal positions. This result indicates that multiple repression activities are combined to exceed critical thresholds on target genes. CtBP mutant proteins unable to bind NAD fail to interact with DNA-bound factors. We show that DNA-binding Gal4-CtBP fusion proteins also require NAD binding for activity, indicating that NAD plays a role in repression at a step subsequent to CtBP recruitment to the promoter.
Sutrias-Grau
Montserrat
M
Department of Biochemistry and Molecular Biology, Michigan State University, 413 Biochemistry, East Lansing, MI 48824-1319, USA.
Arnosti
David N
DN
D000429:Alcohol Oxidoreductases; D000595:Amino Acid Sequence; D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D029721:Drosophila Proteins / Q000378:metabolism* / Q000502:physiology; D009154:Mutation; D009243:NAD / Q000378:metabolism* / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism* / Q000502:physiology*; D015534:Trans-Activators
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; D015534:Trans-Activators; C074089:kni protein, Drosophila; D009243:NAD; D000429:Alcohol Oxidoreductases; C096794:C-terminal binding protein