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CtIP-BRCA1 Complex and MRE11 Maintain Replication Forks in the Presence of Chain Terminating Nucleoside Analogs

CtIP-BRCA1 Complex and MRE11 Maintain Replication Forks in the Presence of Chain Terminating Nucleoside Analogs

Mohiuddin Mohiuddin, Md Maminur Rahman, Julian E Sale, Christopher E Pearson

Nucleic Acids Res. 2019 Apr 8;47(6):2966-2980.

PMID: 30657944

Abstract:

Chain-terminating nucleoside analogs (CTNAs), which cannot be extended by DNA polymerases, are widely used as antivirals or anti-cancer agents, and can induce cell death. Processing of blocked DNA ends, like camptothecin-induced trapped-topoisomerase I, can be mediated by TDP1, BRCA1, CtIP and MRE11. Here, we investigated whether the CtIP-BRCA1 complex and MRE11 also contribute to cellular tolerance to CTNAs, including 2',3'-dideoxycytidine (ddC), cytarabine (ara-C) and zidovudine (Azidothymidine, AZT). We show that BRCA1-/-, CtIPS332A/-/- and nuclease-dead MRE11D20A/- mutants display increased sensitivity to CTNAs, accumulate more DNA damage (chromosomal breaks, γ-H2AX and neutral comets) when treated with CTNAs and exhibit significant delays in replication fork progression during exposure to CTNAs. Moreover, BRCA1-/-, CtIPS332A/-/- and nuclease-dead MRE11D20A/- mutants failed to resume DNA replication in response to CTNAs, whereas control and CtIP+/-/- cells experienced extensive recovery of DNA replication. In summary, we provide clear evidence that MRE11 and the collaborative action of BRCA1 and CtIP play a critical role in the nuclease-dependent removal of incorporated ddC from replicating genomic DNA. We propose that BRCA1-CTIP and MRE11 prepare nascent DNA ends, blocked from synthesis by CTNAs, for further repair.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP7481892-B	2′,3′-Dideoxycytidine		7481-89-2	Price

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