There are eight known E2F family members, named E2F1 to E2F8, each with distinct roles and regulatory mechanisms. E2F1, E2F2, and E2F3 are often referred to as "activating" E2Fs because they promote cell cycle progression and are frequently overexpressed in cancers. On the other hand, E2F4 and E2F5 are considered "repressive" E2Fs, as they are involved in cell cycle exit and differentiation. The balance between these activating and repressive E2Fs is critical for normal cell cycle control, and its disruption can lead to oncogenesis.
