Transcriptional activation by Oct-3: evidence for a specific role of the POU-specific domain in mediating functional interaction with Oct-1.

AUTOR(ES)

Vigano, M A

RESUMO

Oct-3, a member of the POU family of transcription factors, is expressed in pluripotent cells of early mammalian embryos and in undifferentiated embryonal carcinoma cell lines. Using a variety of Oct-3 mutants, we have identified two different domains of Oct-3 which activate transcription in transfected mammalian cells. One of these domains, located in the C-terminal part of the protein, plays a major role in transcriptional activation when Oct-3 is bound to its cognate site, the octamer motif. An Oct-3 mutant containing a single amino acid substitution in the POU homeodomain is unable to bind the octamer target in vitro, yet is still able to activate transcription in an octamer-dependent manner. We provide evidence that transactivation by this mutant involves protein-protein interactions with the ubiquitous octamer binding factor Oct-1. This interaction requires the POU-specific domain of Oct-3 and allows recruitment of Oct-3 to the target promoter even in the absence of Oct-3 DNA binding.

Documentos Relacionados

• Differential in vivo activation of the class II and class III snRNA genes by the POU-specific domain of Oct-1.
• POU proteins bend DNA via the POU-specific domain.
• The Oct-1 POU-specific domain can stimulate small nuclear RNA gene transcription by stabilizing the basal transcription complex SNAPc.
• An altered-specificity mutation in a human POU domain demonstrates functional analogy between the POU-specific subdomain and phage lambda repressor.
• Coactivator OBF-1 Makes Selective Contacts with Both the POU-Specific Domain and the POU Homeodomain and Acts as a Molecular Clamp on DNA