STAT1β is a member of the signal transducers and activators of transcription (STAT) family of proteins that carry out a dual function: signal transduction and activation of transcription. STAT1β transcription factor is specific for the IFN pathway and plays a central role in mediating many, if not all, IFN-dependent biological responses. Presence of STAT1β leads to an efficient antiviral response when cells were infected with virus suggesting that a STAT-dependent pathway is activated following virus infection by endogenously produced IFN. Virus-induced STAT protein translocation from the cytoplasmic compartment can be detected within 3 h of infection.