Unlabelled: Human cytomegalovirus (HCMV) or its immediate-early IE86 protein alone induces cell cycle in quiescent primary human foreskin fibroblasts (HFFs), but blocks its progression at the G1/S interphase and inhibits cellular DNA synthesis by a mechanism that is not clearly understood. It is assumed that, in this phenomenon, the binding of minichromosome maintenance (Mcm) proteins to replication origins is blocked. In this work, we analyzed the initiation of DNA replication in HCMV-permissive U373MG cells and used oriP of Epstein-Barr virus (EBV) as a simplified model of a cellular replication origin. Using U373MG cells we found that HCMV IE86 protein was bound to Mcm3, but did not inhibit the cellular DNA synthesis. Using U373MG-p220.2 cells carrying EBV oriP and expressing Epstein-Barr nuclear antigen 1 (EBNA1), we found that EBNA1 as well as Mcm3 were bound to oriP and that neither HCMV nor IE86 protein inhibited the binding of Mcm3 to oriP. Differences between the effects of HCMV on the cell cycle progression in HFFs and U373MG cells are discussed.
Keywords: cell cycle; Human cytomegalovirus; DNA replication.
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