In Vitro Replication of Chromatin Templates

Eukaryotic genome replication implies that both the DNA and the associated proteins must be duplicated during each S phase. Model systems such as the simian virus 40 (SV40) in vitro replication system have provided important information on the mechanism of DNA replication in mammalian cells (reviewed in ref. 1 ). The SV40 genome is replicated by the host replication machinery in conjunction with a single viral protein, T antigen (T-Ag). Replication of the viral genome begins at the well-defined origin and proceeds in a bidirectional and semidiscontinuous manner. A valuable feature is that SV40 DNA exists in infected cells as minichromosomes which resemble the host cell chromatin. Therefore studies on SV40 DNA replication can address issues such as chromatin replication.