"Interferon Regulatory Factor 1 (IRF-1) a tumor suppressor and an antiviral host factor selectively suppresses an endogenous retroviruses (ERVs) expression. IRF-1 suppresses endogenous reverse transcriptase activity of interferon-beta treated primary macrophages and mouse embryonic fibroblasts. Specific ERV expression is suppressed in both lung and spleen of IRF-1-/- mice."xsd:string