Coaktiverare

Coaktiverare, or transcriptional coactivators, are proteins that enhance transcription of target genes by cooperating with DNA-binding transcription factors. They do not typically bind promoter DNA themselves, but function as scaffolds or enzymatic platforms that bridge transcription factors to the core transcriptional machinery and recruit chromatin-modifying activities. Through these actions they help translate cellular signals into increased RNA synthesis.

Mechanisms commonly involve chromatin remodeling and histone modification, such as histone acetylation by histone acetyltransferases like CBP/p300, which loosens chromatin and promotes transcription. Coactivators also recruit components of the Mediator complex and RNA polymerase II, facilitate enhancer–promoter looping, and coordinate multiple signaling pathways to specific gene programs.

Prominent examples include the p300/CBP family (EP300 and CREBBP), which have intrinsic acetyltransferase activity; steroid receptor coactivators SRC-1, SRC-2, and SRC-3; and the PGC-1 family (PGC-1α/β) that coactivate metabolic regulators such as PPARs. Other coactivators participate through common modules and can interact with a variety of transcription factors.

Coactivators are essential for normal development and physiology, influencing metabolism, growth, and hormone responses. Dysregulation of coactivators is linked to diseases such as cancer and metabolic disorders, making them topics of active research and potential therapeutic targeting.