title: Murine cytomegalovirus induces expression and enzyme activity of cellular dihydrofolate reductase in quiescent cells.
abstract: Murine cytomegalovirus (MCMV) productively infects quiescent fibroblasts in which the levels of nucleoside triphosphate precursors and cell functions involved in DNA metabolism are minimal. It appears that MCMV has evolved molecular pathways in order to ensure the presence of nucleoside triphosphate precursors for the viral DNA polymerase. Here, we report that MCMV infection of quiescent NIH 3T3 cells markedly stimulates transcription, expression and activity of the cellular dihydrofolate reductase (DHFR), a key enzyme in the synthesis of DNA precursors. DHFR stimulation by MCMV is sensitive to UV irradiation and seems to depend on expression of the viral immediate-early protein pp89. Finally, it has been demonstrated that suppression of virus-induced DHFR activity by the specific inhibitor methotrexate prevents MCMV DNA replication. These observations indicate that induction of host cell DHFR activity by MCMV is required for viral DNA synthesis in quiescent fibroblasts.
authors.affiliation: Department of Public Health and Microbiology, Medical School of Torino, University of Torino, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Lembo
authors.forename: A
authors.initials: A
authors.lastname: Angeretti
authors.forename: M
authors.initials: M
authors.lastname: Gariglio
authors.forename: S
authors.initials: S
authors.lastname: Landolfo
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002453:Cell Cycle; D004261:DNA Replication; D004790:Enzyme Induction; D006566:Herpesviridae Infections / Q000201:enzymology* / Q000473:pathology; D051379:Mice; D018146:Muromegalovirus; D013762:Tetrahydrofolate Dehydrogenase / Q000096:biosynthesis*
chemical_list: D013762:Tetrahydrofolate Dehydrogenase