SUMM4 complex couples insulator function and DNA replication timing control
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ABSTRACT: The asynchronous timing of replication of different chromosome domains is essential for eukaryotic genome stability, but the mechanisms establishing replication timing programs remain incompletely understood. Drosophila SNF2-related factor SUUR imparts under-replication (UR) of late-replicating intercalary heterochromatin (IH) domains in polytene chromosomes. SUUR negatively regulates DNA replication fork progression across IH; however, its mechanism of action remains obscure. Here we developed a novel method termed MS-Enabled Rapid protein Complex Identification (MERCI) to isolate a stable stoichiometric native complex SUMM4 that comprises SUUR and a chromatin boundary protein Mod(Mdg4)-67.2. In vitro, Mod(Mdg4) stimulates the ATPase activity of SUUR, although neither SUUR nor SUMM4 can remodel nucleosomes. Mod(Mdg4)-67.2 and SUUR distribution patterns in vivo partially overlap, and Mod(Mdg4) is required for a normal spatiotemporal distribution of SUUR in chromosomes. SUUR and Mod(Mdg4)-67.2 mediate insulator activities of the gypsy mobile element that disrupt enhancer-promoter interactions and establish euchromatin-heterochromatin barriers in the genome. Furthermore, mutations of SuUR or mod(mdg4) reverse the locus-specific UR. These findings reveal that DNA replication can be delayed by a chromatin barrier and thus, uncover a critical role for architectural proteins in replication timing control. They also provide a biochemical link between ATP-dependent motor factors and the activity of insulators in regulation of gene expression and chromatin partitioning.
ORGANISM(S): Drosophila melanogaster
PROVIDER: GSE189421 | GEO | 2022/12/04
REPOSITORIES: GEO
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