Sin3A (the dominant paralog of Sin3 in breast cancer cells [19]) is a chromatin modulator which acts as a molecular scaffold for the assembly of chromatin-modifier enzymes such as HDACs, and it interacts with the Sin3 Interaction domain (SID) of transcription factors through its first and second paired amphipathic domains (PAH), PAH1 and PAH2, respectively. The gene discussed is SIN3A; the disease is breast carcinoma.