Mutations in the AAA1 domain of Yta7/ ATAD2 enhance CENP-A/ Cse4 deposition in Saccharomyces cerevisiae

The chromatin remodelling factor and histone chaperone Yta7 is a member of the ATAD2 family of AAA+ ATPases from Saccharomyces cerevisiae that has in vivo functions consistent with both nucleosome assembly and disassembly activity. At the centromere, Yta7 is required for proper deposition of the centromeric histone H3 variant CENP-A Cse4. Here, we performed a genetic screen to identify suppressors of the defect of a mutation in CENP-A Cse4 that impairs the interaction with the DNA of the centromeric nucleosome (cse4-S135A). This identified two suppressor alleles of YTA7, yta7-R483S and -D518E, that are located in the AAA1 domain of Yta7. The mutant Yta7 variants showed enhanced deposition of CENP-A Cse4 at the centromere and interacted with CENP-A Cse4 and centromeric sequences, indicating that they are hypermorphic alleles with enhanced chromatin assembly activity. Furthermore, the analysis of in vivo interactions between Yta7 and CENP-A Cse4 showed that the two AAA+ domains and the non-canonical bromodomain of Yta7 are necessary and sufficient for interaction with CENP-A Cse4. The screen furthermore revealed a mutation in the chromatin remodeler Fun30 as a suppressor of the centromeric defect of cse4-S135A. Altogether, this work highlights the importance of nucleosome remodelers in establishing centromeric chromatin.