RESUMEN
Human cytomegalovirus (HCMV), a human herpesvirus, is the leading viral cause of birth defects (1,2). In acquired immune deficiency syndrome (AIDS) patients, HCMV can cause severely debilitating colitis and retinitis; it is now an increasingly common cause of life-threatening pneumonitis in transplant patients (3-5). HCMV has a severely restricted host range in culture. It grows efficiently only in primary human diploid fibroblasts (HFF) and a few selected human cell lines (6-9). Monocytes serve as a major reservoir of latent HCMV in humans and HCMV can be grown in vitro in primary monocyte-derived macrophages (M/M) (10-14).
RESUMEN
Transient complementation of human cytomegalovirus (HCMV) oriLyt DNA replication in permissive human diploid cells expressing replication genes under native promoters requires its UL36-38 gene products. Two of the immediate early (IE) proteins encoded by this locus, pUL37x1 and, to a lesser extent, gpUL37, activated expression of HCMV early gene promoter constructions. The other IE protein encoded by the UL36-38 locus, pUL36, and the early product, pUL38, did not transactivate the HCMV early promoter constructions under similar conditions. The acidic domain, common to both pUL37x1 and gpUL37, is required for activation of HCMV early promoter constructions. Conversely, gpUL37 sequences downstream of amino acid 199 are not required for transactivation of viral early promoters. Taken together, these results suggest that the requirement for UL36-38 products for HCMV DNA replication results, at least in part, from the requirement of the transactivation of HCMV early DNA replication promoters by pUL37x1 and, to a lesser extent, by gpUL37 and that the acidic domain is critical for this activity.