The Histone Chaperone FACT Contributes to DNA Replication-Coupled Nucleosome Assembly

• Mutating Spt16 on lysine 692 and arginine 693 impairs interaction of Spt16 and H3-H4
• FACT participates in the deposition of new H3-H4 onto DNA
• Rtt106:H3K56Ac-H4 complexes enhance the loading of H3-H4 onto FACT during S phase

SummaryDNA replication-coupled (RC) nucleosome assembly is mediated by histone chaperones and is fundamental for epigenetic inheritance and maintenance of genomic integrity. The mechanisms that promote this process are only partially understood. Here, we show that the histone chaperone FACT (facilitates chromatin transactions), consisting of Spt16 and Pob3, promotes newly synthesized histone H3-H4 deposition. We describe an allele of Spt16 (spt16-m) that has a defect in binding to H3-H4 and impairs their deposition onto DNA. Consistent with a direct role for FACT in RC nucleosome assembly, spt16-m displays synthetic defects with other histone chaperones associated with this process, CAF-1 and Rtt106. Importantly, we show that FACT physically associates with Rtt106 and that the acetylation of H3K56, a mark on newly synthesized H3, modulates this interaction. Therefore, FACT collaborates with CAF-1 and Rtt106 in RC nucleosome assembly.

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