Figure 4.

MCM origin association correlates with B2 mutant origin function. Strains containing ARS1 mutations were arrested in the G₁ phase of the cell cycle with α factor and assayed for MCM association by ChIP. PCR was performed on both the immunoprecipitated (IPed) DNA and the input DNA with primers to the origins ARS305 and ARS1, and the non-origin sequence URA3. Sample IPed PCR is shown above. The graph represents the quantitation of the (ARS1 IP/ARS1 input)/(ARS305 IP/ARS305 input) for four individual experiments. Origin function is plotted on the second axis. The A element mutation is ARS1/865–872 and does not have a plasmid loss rate because plasmids containing this origin cannot transform. M1–M9 refer to the B2 mutants listed in Table 2.