Figure 2.

Regulation of replication-independent chromatin assembly in extracts from cdc mutants. (A) Assembly is compared in extracts from unsynchronized cells growing at the permissive temperature and from cells arrested at the indicated phases of the cell cycle by temperature shift. Reactions were performed for 30 min at 22°C by using 25, 50, and 100 μg of protein for each extract. The migration of open circular/relaxed DNA (O/R), highly supercoiled species (SC), and intermediate topoisomers (Int.) is indicated. (B) Quantitation of replication-independent chromatin assembly in extracts from cdc15–2 cells synchronized in M phase, released into the cell cycle by shifting to the permissive temperature, and harvested at the indicated time points thereafter. Unshaded regions correspond to transitions between cell cycle stages. Reactions were performed for 30 min at 22°C by using 25 μg of protein for each extract. (C) Time course of supercoiling in extracts from cdc mutants arrested in G₂/M, G₁, and S phase. Reaction conditions as in A.