biostudies-literatureZhu YHHS | National Institutes of HealthHHS | NIH | National Cancer InstituteNCI NIH HHSe2221894120https://www.ebi.ac.uk/biostudies/studies/S-EPMC10288554biostudies-literatureUnknown120(25)The nonhomologous end-joining (NHEJ) pathway is a major DNA double-strand break repair pathway in mammals and is essential for lymphocyte development. Ku70 and Ku80 heterodimer (KU) initiates NHEJ, thereby recruiting and activating the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs). While DNA-PKcs deletion only moderately impairs end-ligation, the expression of kinase-dead DNA-PKcs completely abrogates NHEJ. Active DNA-PK phosphorylates DNA-PKcs at two clusters-PQR around S2056 (S2053 in mouse) and ABCDE around T2609. Alanine substitution at the S2056 cluster moderately compromises end-ligation on plasmid-based assays. But, mice carrying alanine substitution at all five serine residues within the S2056 cluster (<i>DNA-PKcs^PQR/PQR</i>) display no defect in lymphocytProceedings of the National Academy of Sciences of the United States of AmericaPhosphorylation of DNA-PKcs at the S2056 cluster ensures efficient and productive lymphocyte development in XLF-deficient mice.PMC10288554P01 CA174653R01 CA275184P01CA174653R01 CA1580735R01CA158073R01CA275184P30 CA013696Lee BJZha SZhu YJiang WLi AGershik SfalsePhosphorylation of DNA-PKcs at the S2056 cluster ensures efficient and productive lymphocyte development in XLF-deficient mice.The nonhomologous end-joining (NHEJ) pathway is a major DNA double-strand break repair pathway in mammals and is essential for lymphocyte development. Ku70 and Ku80 heterodimer (KU) initiates NHEJ, thereby recruiting and activating the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs). While DNA-PKcs deletion only moderately impairs end-ligation, the expression of kinase-dead DNA-PKcs completely abrogates NHEJ. Active DNA-PK phosphorylates DNA-PKcs at two clusters-PQR around S2056 (S2053 in mouse) and ABCDE around T2609. Alanine substitution at the S2056 cluster moderately compromises end-ligation on plasmid-based assays. But, mice carrying alanine substitution at all five serine residues within the S2056 cluster (<i>DNA-PKcs^PQR/PQR</i>) display no defect in lymphocyt2023-01-01T00:00:00Z2023 Jun2026-07-14T21:56:24.704Z2025-07-06T03:04:28.74ZS-EPMC102885543730744310.1073/pnas.2221894120