A gradient of template dependence defines distinct biological roles for family X polymerases in nonhomologous end joining

Mol Cell. 2005 Aug 5;19(3):357-66. doi: 10.1016/j.molcel.2005.06.012.


Three Pol X family members have been linked to nonhomologous end joining (NHEJ) in mammals. Template-independent TdT promotes diversity during NHEJ-dependent repair of V(D)J recombination intermediates, but the roles of the template-dependent polymerases mu and lambda in NHEJ remain unclear. We show here that pol mu and pol lambda are similarly recruited by NHEJ factors to fill gaps when ends have partially complementary overhangs, suggesting equivalent roles promoting accuracy in NHEJ. However, only pol mu promotes accuracy during immunoglobulin kappa recombination. This distinctive in vivo role correlates with the TdT-like ability of pol mu, but not pol lambda, to act when primer termini lack complementary bases in the template strand. However, unlike TdT, synthesis by pol mu in this context is primarily instructed by a template from another DNA molecule. This apparent gradient of template dependence is largely attributable to a small structural element that is present but different in all three polymerases.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • B-Lymphocytes / metabolism
  • Cell Line
  • DNA / genetics
  • DNA / metabolism
  • DNA Nucleotidylexotransferase / genetics
  • DNA Nucleotidylexotransferase / metabolism
  • DNA Polymerase beta / genetics
  • DNA Polymerase beta / metabolism*
  • DNA Repair
  • DNA-Directed DNA Polymerase / genetics
  • DNA-Directed DNA Polymerase / metabolism*
  • Gene Expression / genetics
  • Gene Rearrangement / genetics
  • Humans
  • Immunoglobulin Joining Region / genetics*
  • Immunoglobulin kappa-Chains / genetics*
  • Mice
  • Models, Molecular
  • Molecular Sequence Data
  • Recombinant Proteins / metabolism
  • Recombination, Genetic / genetics*
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Templates, Genetic
  • Transfection


  • Immunoglobulin Joining Region
  • Immunoglobulin kappa-Chains
  • Recombinant Proteins
  • DNA
  • DNA polymerase beta2
  • DNA polymerase mu
  • DNA Nucleotidylexotransferase
  • DNA Polymerase beta
  • DNA-Directed DNA Polymerase