DNA polymerases eta and kappa exchange with the polymerase delta holoenzyme to complete common fragile site synthesis.
DNA Repair (Amst)
; 57: 1-11, 2017 09.
Article
en En
| MEDLINE
| ID: mdl-28605669
ABSTRACT
Common fragile sites (CFSs) are inherently unstable genomic loci that are recurrently altered in human tumor cells. Despite their instability, CFS are ubiquitous throughout the human genome and associated with large tumor suppressor genes or oncogenes. CFSs are enriched with repetitive DNA sequences, one feature postulated to explain why these loci are inherently difficult to replicate, and sensitive to replication stress. We have shown that specialized DNA polymerases (Pols) η and κ replicate CFS-derived sequences more efficiently than the replicative Pol δ. However, we lacked an understanding of how these enzymes cooperate to ensure efficient CFS replication. Here, we designed a model of lagging strand replication with RFC loaded PCNA that allows for maximal activity of the four-subunit human Pol δ holoenzyme, Pol η, and Pol κ in polymerase mixing assays. We discovered that Pol η and κ are both able to exchange with Pol δ stalled at repetitive CFS sequences, enhancing Normalized Replication Efficiency. We used this model to test the impact of PCNA mono-ubiquitination on polymerase exchange, and found no change in polymerase cooperativity in CFS replication compared with unmodified PCNA. Finally, we modeled replication stress in vitro using aphidicolin and found that Pol δ holoenzyme synthesis was significantly inhibited in a dose-dependent manner, preventing any replication past the CFS. Importantly, Pol η and κ were still proficient in rescuing this stalled Pol δ synthesis, which may explain, in part, the CFS instability phenotype of aphidicolin-treated Pol η and Pol κ-deficient cells. In total, our data support a model wherein Pol δ stalling at CFSs allows for free exchange with a specialized polymerase that is not driven by PCNA.
Palabras clave
Texto completo:
1
Bases de datos:
MEDLINE
Asunto principal:
Antígeno Nuclear de Célula en Proliferación
/
Repeticiones de Microsatélite
/
ADN Polimerasa Dirigida por ADN
/
Replicación del ADN
Tipo de estudio:
Prognostic_studies
Límite:
Humans
Idioma:
En
Revista:
DNA Repair (Amst)
Asunto de la revista:
BIOLOGIA MOLECULAR
/
BIOQUIMICA
Año:
2017
Tipo del documento:
Article
País de afiliación:
Estados Unidos