Koactivators

Koactivators are proteins that play a crucial role in gene expression by interacting with transcription factors. Unlike activators, which directly bind to DNA, koactivators do not have DNA-binding domains themselves. Instead, they are recruited to gene promoters by transcription factors that are already bound to DNA. Once recruited, koactivators can facilitate gene transcription through various mechanisms.

One primary function of koactivators is to recruit or stabilize the basal transcription machinery, which includes RNA polymerase and other general transcription factors, to the promoter. They can also modify chromatin structure, making the DNA more accessible to transcription factors and the transcriptional machinery. This often involves enzymatic activity, such as histone acetyltransferase (HAT) activity, which can loosen the chromatin by acetylating histones. Some koactivators also serve as scaffolds, bringing together multiple proteins involved in transcription regulation into a functional complex.

The precise composition and function of koactivator complexes can vary depending on the specific transcription factor and the target gene. This allows for a fine-tuned regulation of gene expression in response to cellular signals and developmental cues. Dysregulation of koactivator function has been implicated in various diseases, including cancer, highlighting their importance in maintaining normal cellular processes. Understanding koactivators is essential for comprehending the intricate mechanisms of gene regulation.