title: Murine coronavirus replication induces cell cycle arrest in G0/G1 phase.
abstract: Mouse hepatitis virus (MHV) replication in actively growing DBT and 17Cl-1 cells resulted in the inhibition of host cellular DNA synthesis and the accumulation of infected cells in the G(0)/G(1) phase of the cell cycle. UV-irradiated MHV failed to inhibit host cellular DNA synthesis. MHV infection in quiescent 17Cl-1 cells that had been synchronized in the G(0) phase by serum deprivation prevented infected cells from entering the S phase after serum stimulation. MHV replication inhibited hyperphosphorylation of the retinoblastoma protein (pRb), the event that is necessary for cell cycle progression through late G(1) and into the S phase. While the amounts of the cellular cyclin-dependent kinase (Cdk) inhibitors p21(Cip1), p27(Kip1), and p16(INK4a) did not change in infected cells, MHV infection in asynchronous cultures induced a clear reduction in the amounts of Cdk4 and G(1) cyclins (cyclins D1, D2, D3, and E) in both DBT and 17Cl-1 cells and a reduction in Cdk6 levels in 17Cl-1 cells. Infection also resulted in a decrease in Cdk2 activity in both cell lines. MHV infection in quiescent 17Cl-1 cells prevented normal increases in Cdk4, Cdk6, cyclin D1, and cyclin D3 levels after serum stimulation. The amounts of cyclin D2 and cyclin E were not increased significantly after serum stimulation in mock-infected cells, whereas they were decreased in MHV-infected cells, suggesting the possibility that MHV infection may induce cyclin D2 and cyclin E degradation. Our data suggested that a reduction in the amounts of G(1) cyclin-Cdk complexes in MHV-infected cells led to a reduction in Cdk activities and insufficient hyperphosphorylation of pRb, resulting in inhibition of the cell cycle in the G(0)/G(1) phase.
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, MRB 4.146, 301 University Blvd., Galveston, TX 77555-1019, USA.
authors.forename: Chun-Jen
authors.initials: CJ
authors.lastname: Chen
authors.forename: Shinji
authors.initials: S
authors.lastname: Makino
mesh_terms: D000818:Animals; D042846:CDC2-CDC28 Kinases / Q000032:analysis; D002455:Cell Division; D051357:Cyclin-Dependent Kinase 2; D004247:DNA / Q000096:biosynthesis; D016193:G1 Phase; D051379:Mice; D006517:Murine hepatitis virus / Q000502:physiology*; D010766:Phosphorylation; D016192:Resting Phase, Cell Cycle; D016160:Retinoblastoma Protein / Q000378:metabolism; D014779:Virus Replication
chemical_list: D016160:Retinoblastoma Protein; D004247:DNA; D042846:CDC2-CDC28 Kinases; C495893:Cdk2 protein, mouse; D051357:Cyclin-Dependent Kinase 2