Abstract
Nuclear and cytoplasmic RNAs, synthesized in cells productively infected with human cytomegalovirus (HCMV) were analysed at various times after infection by liquid and filter DNA-RNA hybridization. Results of these experiments have revealed that: (i) the fraction of the genome transcribed increased as infection progressed. In the nucleus, transcripts represented approx. 20% of the virus DNA sequences at both 2 and 4 h post-infection (p.i.) and 36% of the virus DNA at 40 h p.i; (ii) the increase in virus sequences among nuclear transcripts at late times was prevented by the DNA synthesis inhibitor, 2'-deoxyfluorouridine; (iii) early virus RNA transcripts were subset of those represented in late RNA; (iv) two classes of early RNA were identified by competition hybridization; (v) approx. 10% of the late nuclear transcripts were symmetrical. Results of filter hybridization at DNA excess indicated that virus-specific RNA represented 0.6% of RNA labelled from 0 to 2 h p.i., and 1.8% of RNA labelled from 28 to 30 h. Polyadenylated RNA isolated from cytoplasm represented 1.2% and 10% of labelled mRNA at 2 h and 30 h respectively. Our data show that during productive infection of human cells by HCMV, gene expression is under temporal, quantitative and post-transcriptional control.
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