DNA-dependent protein kinase activity is not required for immunoglobulin class switching.
Class switch recombination (CSR), similar to V(D)J recombination, is thought to involve DNA double strand breaks and repair by the nonhomologous end-joining pathway. A key component of this pathway is DNA-dependent protein kinase (DNA-PK), consisting of a catalytic subunit (DNA-PKcs) and a DNA-binding heterodimer (Ku70/80). To test whether DNA-PKcs activity is essential for CSR, we examined whether IgM(+) B cells from scid mice with site-directed H and L chain transgenes were able to undergo CSR. Although B cells from these mice were shown to lack DNA-PKcs activity, they were able to switch from IgM to IgG or IgA with close to the same efficiency as B cells from control transgenic and nontransgenic scid/+ mice, heterozygous for the scid mutation. We conclude that CSR, unlike V(D)J recombination, can readily occur in the absence of DNA-PKcs activity. We suggest nonhomologous end joining may not be the (primary or only) mechanism used to repair DNA breaks during CSR.
Bosma
Gayle C
GC
Institute for Cancer Research, Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111, USA.
Kim
Jiyoon
J
Urich
Teresa
T
Fath
Donna M
DM
Cotticelli
Maria G
MG
Ruetsch
Norman R
NR
Radic
Marko Z
MZ
Bosma
Melvin J
MJ
D000818:Animals; D001402:B-Lymphocytes; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins; D005803:Genes, Immunoglobulin; D007108:Immune Tolerance; D007070:Immunoglobulin A / Q000096:biosynthesis; D017578:Immunoglobulin Class Switching; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000097:blood / Q000145:classification; D015847:Interleukin-4 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011995:Recombination, Genetic; D013601:T-Lymphocytes / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D004268:DNA-Binding Proteins; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D016212:Transforming Growth Factor beta; D015847:Interleukin-4; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases