Alexa Fluor^® 488 Mouse Anti-Human Rb (pS780) Antibody (S-3521)

Phospho-Rb (Ser780) refers to the specific modification state of the Retinoblastoma protein (Rb) phosphorylated at its serine 780 residue. The Rb protein is a critical negative regulator of the cell cycle. In its unphosphorylated or hypophosphorylated state, it binds to and inhibits the transcription factor E2F, thereby blocking cell cycle progression from the G1 phase to the S phase. When cells receive pro-proliferative signals, the cyclin-dependent kinase 4/6-cyclin D complex (CDK4/6-cyclin D) specifically catalyzes the phosphorylation of multiple sites on the Rb protein, including Ser780. Phosphorylation at Ser780 is an early and key event during G1 phase progression. It directly induces a conformational change in the Rb protein, causing its dissociation from E2F. Subsequently, E2F activates the transcription of a set of genes essential for S phase, driving DNA replication and cell cycle advancement. Therefore, the detection of Phospho-Rb (Ser780) levels is commonly used as an important molecular marker for assessing CDK4/6 kinase activity, cell proliferation status, and the G1/S transition. It is widely applied in cancer research (e.g., evaluating the efficacy of CDK4/6 inhibitors in breast cancer treatment) and studies on cell cycle regulatory mechanisms.