Coordination of histone chaperones for parental histone segregation and epigenetic inheritance
Chromatin-based epigenetic memory relies on the accurate distribution of parental histone tetramers to newly replicated DNA strands, serving as templates for chromatin structure duplication. Mcm2, a subunit of the replicative helicase, and the Dpb3/4, subunits of polymerase epsilon, govern parental histone deposition to the lagging and leading strands, respectively. However, their contribution to epigenetic inheritance remains controversial. Here we show in fission yeast that a Mcm2 histone chaperone mutation severely disrupts heterochromatin inheritance, while Dpb3/4 mutations cause only moderate defects. Surprisingly, simultaneous Mcm2 and Dpb3/4 mutations stabilizes heterochromatin inheritance. eSPAN analyses confirm the conservation of Mcm2 and Dpb3/4 functions in parental histone segregation, with their collective absence reducing segregation bias. Furthermore, the FACT histone chaperone also regulates parental histone transfer independently of strands and collaborates with Mcm2 and Dpb3/4 to maintain parental histone density, ensuring faithful heterochromatin inheritance. These results underscore the importance of precise parental histone segregation to the lagging strand for epigenetic inheritance and unveil unique properties of parental histone chaperones during DNA replication. Overall design: Input, BrdU, H3K56ac ChIP-Seq, H3K56ac eSPAN, H3K4me3 ChIP-Seq, H3K4me3 eSPAN, are performed in S.pombe followed by Next Generation Sequencing