Human cytomegalovirus infection induces cellular thymidylate synthase gene expression in quiescent fibroblasts.
Productive infection of non-proliferating cells by cytomegalovirus (CMV) requires the coordinated stimulation of host biochemical pathways that prepare cells to synthesize DNA. Here we illustrate the ability of human CMV (HCMV) to stimulate cellular thymidylate synthase (TS) gene expression in quiescent human embryonic lung fibroblasts. TS mRNA and protein levels are nearly undetectable in quiescent cells, but are greatly increased following HCMV infection. Inhibition of TS activity was shown to impair HCMV DNA synthesis, demonstrating that TS upregulation is required for efficient HCMV replication in quiescent cells. The increase in TS gene expression was due to an increase in gene transcription, since the expression of a reporter gene driven by the human TS promoter was strongly induced by HCMV infection. Deletion analysis of the human TS promoter identified two positive elements that are important for this increased transcription. We have previously shown that murine CMV (MCMV) stimulates the mouse TS promoter by a mechanism that depends on the presence of an E2F element in the promoter region. However, deletion of the two potential E2F binding sites in the human TS promoter did not prevent the virus-induced increase in TS promoter activity. Our data suggest that HCMV activates human TS gene transcription by mechanisms that are independent of E2F and different from those used by MCMV to stimulate the mouse TS promoter.
Gribaudo
Giorgio
G
Department of Public Health and Microbiology, University of Torino, Via Santena, 9 - 10126 Torino, Italy1.
Riera
Ludovica
L
Department of Public Health and Microbiology, University of Torino, Via Santena, 9 - 10126 Torino, Italy1.
Rudge
Thomas L
TL
Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA2.
Caposio
Patrizia
P
Department of Public Health and Microbiology, University of Torino, Via Santena, 9 - 10126 Torino, Italy1.
Johnson
Lee F
LF
Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA2.
Landolfo
Santo
S
Department of Public Health and Microbiology, University of Torino, Via Santena, 9 - 10126 Torino, Italy1.
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003587:Cytomegalovirus / Q000472:pathogenicity*; D003586:Cytomegalovirus Infections / Q000821:virology*; D004261:DNA Replication; D005347:Fibroblasts / Q000502:physiology / Q000821:virology*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D018146:Muromegalovirus / Q000472:pathogenicity; D011401:Promoter Regions, Genetic / Q000235:genetics; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D015533:Transcriptional Activation; D015854:Up-Regulation
D013940:Thymidylate Synthase