Open AccessArtemis-independent functions of DNA-dependent protein kinase in Ig heavy chain class switch recombination and development
Author(s) -
Sean Rooney,
Frederick W. Alt,
JoAnn Sekiguchi,
John P. Manis
Publication year - 2005
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.0409857102
Subject(s) - dna pkcs , non homologous end joining , microbiology and biotechnology , ku80 , biology , v(d)j recombination , dna , ku70 , dna repair protein xrcc4 , immunoglobulin class switching , gene , dna repair , genetics , dna binding protein , b cell , recombination , transcription factor , antibody , dna mismatch repair
Assembly of Ig genes in B lineage cells involves two distinct DNA rearrangements. In early B cell development, site-specific double strand breaks (DSBs) at germ-line V, D, and J gene segments are joined via nonhomologous end-joining (NHEJ) to form variable region exons. Activated mature B cells can change expressed Ig heavy chain constant region exons by class switch recombination (CSR), which also involves DSB intermediates. Absence of any known NHEJ factor severely impairs joining of cleaved V, D, and J segments. In NHEJ, DNA-dependent protein kinase (DNA-PK), which is comprised of the Ku70/80 end-binding heterodimer and the catalytic subunit (DNA-PKcs), activates Artemis to generate a nuclease that processes DSBs before ligation. Because inactivation of DNA-PKcs components also severely affects CSR, we tested whether DNA-PK also functions in CSR via activation of Artemis. To obviate the requirement for V(D)J recombination, we generated DNA-PKcs- and Artemis-deficient B cells that harbored preassembled Ig heavy chain and kappa-light chain "knock-in" (HL) alleles. We found that Artemis-deficient HL B cells undergo robust CSR, indicating that DNA-PKcs functions in CSR via an Artemis-independent mechanism. To further elucidate potential Artemis-independent functions of DNA-PKcs, we asked whether the embryonic lethality associated with double-deficiency for DNA-PKcs and the related ataxia-telangiectasia-mutated (ATM) kinase was also observed in mice doubly deficient for ATM and Artemis. We found that ATM/Artemis double-deficient mice were viable and born in normal Mendelian numbers. Therefore, we conclude that DNA-PKcs has Artemis-independent functions in CSR and normal development.