Biology subjects

McKinzey, D. R.

Publications and source records attributed to McKinzey, D. R..

4 recordsLinked to original sources

bioRxiv2026

Host DNA repair factors empower a mechanism of antiviral nucleoside analog resistance

How host functions affect resistance to antiviral drugs is poorly understood. Ganciclovir, a chain-terminating nucleoside analog, is a first-line therapy against human cytomegalovirus, a widespread herpesvirus that causes life-threatening disease in immunocompromised individuals and newborns. Ganciclovir resistance, which is caused by mutations that affect the viral kinase, UL97 and/or the viral polymerase, UL54, can cause treatment failures. Among these mutations, those reducing the exonuclease activity of the viral DNA polymerase permit ganciclovir incorporation without chain termination. However, the fate of DNA strands containing the incorporated nucleotide analog is unknown. We show here that template DNA containing ganciclovir fails to support DNA synthesis of the complementary strand by exonuclease-mutant polymerase. Moreover, while DNA synthesis and ganciclovir incorporation are limited in drug-treated fibroblasts infected by virus with wild-type polymerase, an exonuclease-resistant mutant virus can better synthesize full-length genomes and incorporate substantially more ganciclovir into DNA. Notably, ganciclovir is lost from DNA when drug is removed, suggesting that ganciclovir-containing templates are repaired. We identify the host nucleotide excision repair component, XPA, and the repair enzyme, polymerase kappa, as each being necessary for mutant virus ganciclovir resistance and polymerase kappa as being required for the mutants cidofovir resistance, demonstrating a role for host DNA repair machinery in a mechanism of antiviral resistance. We propose a model for this mechanism, which has relevance for at least one other antiviral drug and likely other nucleoside analog therapeutics, and highlights the participation of host DNA repair machinery during human cytomegalovirus DNA replication. IMPORTANCENucleoside analogues such as ganciclovir, which is a leading drug for preventing and treating human cytomegalovirus, are a critical defense against viral diseases, but antiviral resistance often results in treatment failures. This study reveals a critical role for host DNA repair in a mechanism of resistance to ganciclovir, and identifies at least one specific repair pathway that permits viral DNA synthesis in the presence of ganciclovir, defining a mechanism by which cellular DNA repair pathways conspire to enable antiviral drug resistance. This mechanism is relevant to at least one other antiviral drug and may apply to other antiviral and anticancer agents. The study also showcases the participation of host DNA repair machinery during human cytomegalovirus DNA synthesis.

microbiology↗

bioRxiv2026

Structural Activation of DNA Unwinding by MCM8/9/HROB

The minichromosomal maintenance MCM8 and MCM9 proteins form a heterohexameric complex that acts to unwind or remodel duplex DNA in DNA recombination and repair pathways. Mutations or absence of MCM8/9 have been linked to infertility, sex-specific deficiencies, and several cancers. Recently, HROB has been identified as a critical cofactor of MCM8/9; however, the mechanism underlying activation of MCM8/9 DNA binding and unwinding remain unclear. Here, we present dynamic structures of MCM8/9 with DNA, HROB and ATP analogs using cryo-electron microscopy. DNA binding induces a pronounced rotational rearrangement between the N-terminal DNA binding and C-terminal AAA+ ATPase domains, reorganizing DNA-binding loops into a staircase configuration that supports DNA engagement. Remarkably, HROB associates with both halves of the heterohexamer and drives a similar rotation prior DNA binding for localizing MCM8/9 to sites of crosslink damage and unwinding, culminating in a unified mechanistic model for MCM8/9 helicase function and its activation by HROB.

biochemistry↗

bioRxiv2021

A novel multi-functional role for the MCM8/9 helicase complex in maintaining fork integrity during replication stress

The minichromosome maintenance (MCM) 8/9 helicase is a AAA+ complex involved in DNA replication-associated repair. Despite high sequence homology to the MCM2-7 helicase, an active role for MCM8/9 has remained elusive. We interrogated fork progression in cells lacking MCM8 or 9 and find there is a functional partitioning. Loss of MCM8 or 9 slows overall replication speed and increases markers of genomic damage and fork instability, further compounded upon treatment with hydroxyurea. MCM8/9 acts upstream and antagonizes the recruitment of BRCA1 in nontreated conditions. However, upon treatment with fork stalling agents, MCM9 recruits Rad51 to protect and remodel persistently stalled forks. The helicase function of MCM8/9 aids in normal replication fork progression, but upon excessive stalling, MCM8/9 directs additional stabilizers to protect forks from degradation. This evidence defines novel multifunctional roles for MCM8/9 in promoting normal replication fork progression and promoting genome integrity following stress.

cell biology↗

bioRxiv2020

Motifs of the C-terminal Domain of MCM9 Direct Localization to Sites of Mitomycin-C Damage for RAD51 Recruitment

The MCM8/9 complex is implicated in aiding fork progression and facilitating homologous recombination (HR) in response to several DNA damage agents. MCM9 itself is an outlier within the MCM family containing a long C-terminal extension (CTE) comprising 42% of the total length, but with no known functional components and high predicted disorder. In this report, we identify and characterize two unique motifs within the primarily unstructured CTE that are required for localization of MCM8/9 to sites of mitomycin C (MMC) induced DNA damage. First, an unconventional bipartite-like nuclear localization (NLS) motif consisting of two positively charged amino acid stretches separated by a long intervening sequence is required for the nuclear import of both MCM8 and MCM9. Second, a variant of the BRC motif (BRCv), similar to that found in other HR helicases, is necessary for localization to sites of MMC damage. The MCM9-BRCv directly interacts with and recruits RAD51 downstream to MMC-induced damage to aid in DNA repair. Patient lymphocytes devoid of functional MCM9 and discrete MCM9 knockout cells have a significantly impaired ability to form RAD51 foci after MMC treatment. Therefore, the disordered CTE in MCM9 is functionally important in promoting MCM8/9 activity and in recruiting downstream interactors; thus, requiring full length MCM9 for proper DNA repair.

biochemistry↗