BTG Family Member-2 (BTG2) is endowed with antiproliferative activity. The expression of BTG2 in cycling cells induces accumulation of hypophosphorylated, growth-inhibitory forms of Retinoblastoma protein(Rb) and lead to G1 arrest through impairment of DNA synthesis. Rb is a nuclear phosphoprotein whose phosphorylation state oscillates regularly during the cell cycle. Hypophosphorylated Rb associates with members of the E2F family of transcription factors, impairing their activity and leading to a cell cycle block in G1. Conversely, the phosphorylation of Rb inactivates its growth suppression activity by freeing E2F molecules, thus enabling them to transactivate genes required for the progression of the cell into S phase and the remainder of the cell cycle. Cyclin-dependent kinases (CDKs) are the molecules responsible for Rb phosphorylation and its consequent inactivation.

BTG Family Proteins and Cell Cycle Regulation References