Mta2 promotes Tipin-dependent maintenance of replication fork integrity.
Orderly progression of S phase requires the action of replisome-associated Tipin and Tim1 proteins, whose molecular function is poorly understood. Here, we show that Tipin deficiency leads to the accumulation of aberrant replication intermediates known as reversed forks. We identified Mta2, a subunit of the NuRD chromatin remodeler complex, as a novel Tipin binding partner and mediator of its function. Mta2 is required for Tipin-dependent Polymerase α binding to replicating chromatin, and this function is essential to prevent the accumulation of reversed forks. Given the role of the Mta2-NuRD complex in the maintenance of heterochromatin, which is usually associated with hard-to-replicate DNA sequences, we tested the role of Tipin in the replication of such regions. Using a novel assay we developed to monitor replication of specific genomic loci in Xenopus laevis egg extract we demonstrated that Tipin is directly required for efficient replication of vertebrate centromeric DNA. Overall these results suggest that Mta2 and Tipin cooperate to maintain replication fork integrity, especially on regions that are intrinsically difficult to duplicate.
Genome Stability Laboratory; London Research Institute; South Mimms, UK; 2The FIRC Institute of Molecular Oncology (IFOM) Foundation; Milan, Italy.
Alessia
A
Errico
Genome Stability Laboratory; London Research Institute; South Mimms, UK; 2The FIRC Institute of Molecular Oncology (IFOM) Foundation; Milan, Italy.
Antoine
A
Aze
Genome Stability Laboratory; London Research Institute; South Mimms, UK; 2The FIRC Institute of Molecular Oncology (IFOM) Foundation; Milan, Italy.
Vincenzo
V
Costanzo
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002503:Centromere / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004247:DNA / Q000378:metabolism*; D004256:DNA Polymerase I / Q000378:metabolism; D004261:DNA Replication / Q000502:physiology*; D004268:DNA-Binding Proteins; D056426:Genetic Loci; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
D002352:Carrier Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D029867:Xenopus Proteins; C524402:tipin protein, Xenopus; D004247:DNA; D004256:DNA Polymerase I; C000594833:MTA2 protein, Xenopus; D056245:Mi-2 Nucleosome Remodeling and Deacetylase Complex
DNA replication; Xenopus laevis; centromeres; heterochromatin; histone deacetylase; replicaiton fork integrity