Terminal deoxynucleotidyltransferase: the story of an untemplated DNA polymerase capable of DNA bridging and templated synthesis across strands

Curr Opin Struct Biol. 2018 Dec:53:22-31. doi: 10.1016/j.sbi.2018.03.019. Epub 2018 Apr 12.


Terminal deoxynucleotidyltransferase (TdT) is a member of the polX family which is involved in DNA repair. It has been known for years as an untemplated DNA polymerase used during V(D)J recombination to generate diversity at the CDR3 region of immunoglobulins and T-cell receptors. Recently, however, TdT was crystallized in the presence of a complete DNA synapsis made of two double-stranded DNA (dsDNA), each with a 3' protruding end, and overlapping with only one micro-homology base-pair, thus giving structural insight for the first time into DNA synthesis across strands. It was subsequently shown that TdT indeed has an in trans template-dependent activity in the presence of an excess of the downstream DNA duplex. A possible biological role of this dual activity is discussed.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • DNA Nucleotidylexotransferase* / chemistry
  • DNA Nucleotidylexotransferase* / metabolism
  • DNA Nucleotidylexotransferase* / physiology
  • DNA Repair
  • DNA Repair Enzymes / physiology
  • DNA-Directed DNA Polymerase / chemistry
  • Humans
  • V(D)J Recombination


  • DNA polymerase X
  • DNA polymerase mu
  • DNA Nucleotidylexotransferase
  • DNA-Directed DNA Polymerase
  • DNA Repair Enzymes