Northern hybridizations were carried out using mRNA preparations of human cytomegalovirus (HCMV)-infected cultures and gene-specific antisense RNA probes for transcriptional analysis of the gene cluster composed of genes for DNA polymerase, glycoprotein B (gB), herpes simplex virus-infected cell protein 18.5 homologue p130 and a major DNA-binding protein corresponding to open reading frames (ORFs) UL54-UL57, respectively.