Despite the limited genetic content of microRNAs, their pervasive role in controlling normal and pathology-associated cellular processes has become firmly established in recent years. The importance of microRNA dysregulation in cancer is well appreciated, and a number of oncomirs and tumor suppressor microRNAs have been identified (15). As a member of the oncomir class of microRNAs, miR-155 is implicated in lymphomagenesis and a wide array of nonlymphoid tumors including breast, colon, and lung (7,16,24,39,42,43). Despite strong evidence implicating miR-155 in cancer etiology, the mechanisms through which miR-155 supports the tumor phenotype are unclear, possibly due to limited knowledge of how predicted targets may be involved in the phenotypic properties of cancer. On the other hand, miR-155's roles in normal immune cell development and the adaptive immune response are much better understood (33, 41). These studies have demonstrated a critical role for miR-155 in immune cell activation and maturation. This evidence and other work (8, 40) have identified critical miR-155 targets whose downregulation is required for these processes.The Epstein-Barr virus (EBV) is a human DNA tumor virus that contributes to lymphoid and epithelial cell malignancies. As a herpesvirus, a unique aspect of the EBV infection cycle is the ability to exist in either a lytic replicative state or in a latent state in which no virus is produced. Depending in part on cell background, EBV utilizes multiple forms of latency gene expression programs. True latency and type I latency are defined by the expression of no protein coding genes or by expression of the episomal replication factor EBNA1 only. Type II latency is defined by the expression of EBNA1 and the latent membrane proteins, LMP1 and/or LMP2, and is the predominant form observed in epithelial tissues. Type III latency refers to expression of the full repertoire of latency genes, which are highly tumorigenic and are capable of growth-transforming naïve resting B cells. While this form of latency is not well tolerated in immunocompetent individuals except during early stages of infection (prior to the development of adaptive immunity to these proteins), type III latency-associated lymphoid malignancies are common in immunocompromised individuals. Expression of type III latency genes in B cells mimics antigen-dependent B-cell activation, and accompanying this activation is a substantial induction of miR-155 expression (17,20,23,29,44). While it is reasonable to assume that induction of miR-155 by the type III latency program plays a role in EBV-mediated B-cell activation and oncogenesis, little is known regarding the role of miR-155 in the virus life cycle or its tumorpromoting activities.Originally identified as cytokines critically involved in the regulation of osteogenic differentiation, bone morphogenetic proteins (BMPs) are now appreciated as having critical functions in a vast number of developmental processes. Dysregulation of BMP signaling is also implicated in disease states ...