RESUMEN
DNA double-strand break (DSB) repair is essential for maintaining our genomes. Mre11-Rad50-Nbs1 (MRN) and Ku70-Ku80 (Ku) direct distinct DSB repair pathways, but the interplay between these complexes at a DSB remains unclear. Here, we use high-throughput single-molecule microscopy to show that MRN searches for free DNA ends by one-dimensional facilitated diffusion, even on nucleosome-coated DNA. Rad50 binds homoduplex DNA and promotes facilitated diffusion, whereas Mre11 is required for DNA end recognition and nuclease activities. MRN gains access to occluded DNA ends by removing Ku or other DNA adducts via an Mre11-dependent nucleolytic reaction. Next, MRN loads exonuclease 1 (Exo1) onto the free DNA ends to initiate DNA resection. In the presence of replication protein A (RPA), MRN acts as a processivity factor for Exo1, retaining the exonuclease on DNA for long-range resection. Our results provide a mechanism for how MRN promotes homologous recombination on nucleosome-coated DNA.
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Roturas del ADN de Doble Cadena , Enzimas Reparadoras del ADN/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas Nucleares/metabolismo , Nucleosomas/enzimología , Reparación del ADN por Recombinación , Imagen Individual de Molécula , Ácido Anhídrido Hidrolasas , Proteínas de Ciclo Celular/genética , Aductos de ADN/genética , Aductos de ADN/metabolismo , Enzimas Reparadoras del ADN/genética , Proteínas de Unión al ADN/genética , Difusión , Exodesoxirribonucleasas/genética , Exodesoxirribonucleasas/metabolismo , Humanos , Autoantígeno Ku/genética , Autoantígeno Ku/metabolismo , Proteína Homóloga de MRE11 , Microscopía Fluorescente , Proteínas Nucleares/genética , Nucleosomas/genética , Factores de TiempoRESUMEN
BACKGROUND: Beginning in July 2016, transgender service members in the US military were allowed to receive gender-affirming medical care, if so desired. OBJECTIVE: This study aimed to evaluate variation in time-to-hormone therapy initiation in active duty Service members after the receipt of a diagnosis indicative of gender dysphoria in the Military Health System. RESEARCH DESIGN: This retrospective cohort study included data from those enrolled in TRICARE Prime between July 2016 and December 2021 and extracted from the Military Health System Data Repository. PARTICIPANTS: A population-based sample of US Service members who had an encounter with a relevant International Classification of Diseases 9/10 diagnosis code. MEASURES: Time-to-gender-affirming hormone initiation after diagnosis receipt. RESULTS: A total of 2439 Service members were included (M age 24 y; 62% white, 16% Black; 12% Latine; 65% Junior Enlisted; 37% Army, 29% Navy, 25% Air Force, 7% Marine Corps; 46% first recorded administrative assigned gender marker female). Overall, 41% and 52% initiated gender-affirming hormone therapy within 1 and 3 years of diagnosis, respectively. In the generalized additive model, time-to-gender-affirming hormone initiation was longer for Service members with a first administrative assigned gender marker of male relative to female ( P <0.001), and Asian and Pacific Islander ( P =0.02) and Black ( P =0.047) relative to white Service members. In time-varying interactions, junior enlisted members had longer time-to-initiation, relative to senior enlisted members and junior officers, until about 2-years postinitial diagnosis. CONCLUSION: The significant variation and documented inequities indicate that institutional data-driven policy modifications are needed to ensure timely access for those desiring care.