The early region of the double-stranded DNA genome of MCPyV encodes the large T antigen (LT), small T antigen (sT), and 57 kT antigen (57kT).12 Both LT and sT inhibit growth suppression by interfering with pRb and p53, respectively.13 Integration often leads to tumor-specific truncation mutations that sustain the expression of sT and truncated large T antigen (LTT) mutants, which retain the critical N-terminal RB-binding LXCXE motif. The gene discussed is RB1; the disease is neoplasm.