INHIBITION OF E2F-MEDIATED TRANSCRIPTION BY P202

Many of the antimicrobial, immunomodulatory and cell growth inhibitory activities of the interferons are mediated by interferon-inducible pr oteins. Earlier we characterized an interferon-inducible murine protei n, p202, whose expression in transfected cells inhibits cell prolifera tion and which can form a complex,vith retinoblastoma protein (pRb). H ere we report that in transfected cells expression of p202 inhibits E2 F-stimulated transcription of a reporter gene and of endogenous genes. Inhibition of the transcriptional activity of E2F by p202 does not de pend on fully functional pRb and is correlated with inhibition of the sequence-specific DNA binding of E2F. p202 interacts with the transcri ption factor E2F (E2F-1/DP-1) in vitro and in vivo. Inhibition of E2F activity by p202 may contribute to growth inhibition by the interferon s.