E2Faktiivisuus

E2Faktiivisuus refers to the activity of E2F transcription factors. E2Fs are a family of proteins that play a crucial role in the regulation of cell cycle progression and the control of gene expression. They are particularly important for the transition from the G1 phase to the S phase of the cell cycle, which is the period of DNA synthesis.

There are multiple E2F family members, with E2F1, E2F2, and E2F3 often considered the "activator" E2Fs, while E2F4, E2F5, E2F6, E2F7, and E2F8 are often considered the "repressor" E2Fs. Activator E2Fs typically bind to promoters of genes required for DNA replication and cell cycle progression, thereby promoting their transcription. Repressor E2Fs, on the other hand, can bind to similar DNA sites but often recruit corepressor complexes, leading to gene silencing.

The activity of E2Fs is tightly regulated, primarily through their interaction with retinoblastoma protein (Rb) and its related pocket proteins (p107, p130). In quiescent or early G1 phase cells, Rb binds to E2F, forming a complex that represses E2F target gene transcription. As the cell cycle progresses and mitogenic signals are received, cyclin-dependent kinases (CDKs) phosphorylate Rb. This phosphorylation causes Rb to release E2F, allowing it to activate the transcription of genes necessary for cell cycle entry and DNA synthesis.

Dysregulation of E2F activity is implicated in various cellular processes, including cancer development. Uncontrolled E2F activation can lead to inappropriate cell proliferation, a hallmark of cancer. Conversely, impaired E2F function can hinder cell proliferation and wound healing. Research into E2F activity is ongoing to better understand its role in normal development and disease.