Histone Modification Governs the Cell Cycle Regulation of a Replication-Independent Chromatin Assembly Pathway in Saccharomyces cerevisiae

We describe a replication-independent, cell cycle-regulated chromatin assembly pathway in budding yeast. The activity of this pathway is low in S phase extracts but is very high in G₂, M, and G₁ cell extracts, with peak activity in late M/early G₁. The cell cycle regulation of this pathway requires a specific pattern of posttranslational modification of histones H3 and/or H4, which is distinct for H3/H4 present in S phase versus M and G₁ phase cell extracts. Histone H3/H4 modification is therefore important for the reciprocal control of replication-dependent and -independent chromatin assembly pathways during the cell cycle.