Abstract
Eukaryotic genomes are duplicated from thousands of replication origins that fire sequentially forming a defined spatiotemporal pattern of replication clusters. The importance of the organization of replisomes into functional clusters, also called replication factories, is still poorly understood. Here we identified the multifunctional protein RIF1 as a structural component of replication factories. RIF1 depletion did not impair the velocity of replication forks, neither in basic conditions nor in presence of a molecule that interferes with replication fork progression but increased the frequency of DNA lesions induced in S phase. Isolation of replication-associated proteins from RIF1-depleted cells revealed a major defect in the clustering of replication factors on nascent DNA, without any noticeable impact on DNA synthesis or replisome stability. We found that the changes in replication patterns commonly observed upon RIF1 depletion are induced by DNA replication stress. The data suggest that RIF1 encases replication factories to ensure the organization of replication clusters against chromatin rearrangements induced by DNA replication stress.
