Epstein Barr virus (EBV) is a human herpesvirus associated with development of several types of lymphoid and epithelial malignancies. EBV infects and transforms B lymphocytes, converting them to an immortalized, continuously proliferating state. During such infection, EBV remains in a latent state during which no progeny virions are produced and the viral DNA remains in a relatively quiescent extrachromosomal form in the nucleus of the host cell. Intermittent reactivation may occur, during which a temporally coordinated cascade of gene expression occurs, leading to replication of the viral DNA, production of infectious virions and lysis of the host cell. One of the viral proteins essential for this process of lytic replication is known as EBV SM protein. There are homologous proteins in all human herpesviruses and all affect various aspects of viral and possibly host RNA processing. We are studying the mechanism by which these proteins enhance RNA accumulation, the basis of target mRNA specificity, and possible effects on RNA stability and nuclear export.