文摘
Signal transduction pathways are frequently found to repress transcription of target genes inthe absence of stimulation and, conversely, to upregulate transcription in the presence of a signal.Transcription factors are central in this dual regulatory mechanism and widely use a generalized mechanismto repress transcription through recruitment of a Sin3-histone deacetylase (HDAC) complex to theirbinding sites on DNA. The protein SAP18 (Sin3-associated polypeptide of 18 kDa) has been shown toplay a key role in gene-specific recruitment of the HDAC complex by a number of transcription factorsincluding Gli, GAGA, and Bicoid. The solution structure of SAP18 reveals a ubiquitin-like fold withseveral large loop insertions relative to other family members. This fold supports the functional role ofSAP18 as a protein-protein adapter module and provides insight for how SAP18 may bridge the Sin3-HDAC complex to transcription factors.