title: Functional analyses of polymorphic variants of human terminal deoxynucleotidyl transferase.
abstract: Human terminal deoxynucleotidyl transferase (hTdT) is a DNA polymerase that functions to generate diversity in the adaptive immune system. Here, we focus on the function of naturally occurring single-nucleotide polymorphisms (SNPs) of hTdT to evaluate their role in genetic-generated immune variation. The data demonstrate that the genetic variations generated by the hTdT SNPs will vary the human immune repertoire and thus its responses. Human TdT catalyzes template-independent addition of nucleotides (N-additions) during coding joint formation in V(D)J recombination. Its activity is crucial to the diversity of the antigen receptors of B and T lymphocytes. We used in vitro polymerase assays and in vivo human cell V(D)J recombination assays to evaluate the activity and the N-addition levels of six natural (SNP) variants of hTdT. In vitro, the variants differed from wild-type hTdT in polymerization ability with four having significantly lower activity. In vivo, the presence of TdT varied both the efficiency of recombination and N-addition, with two variants generating coding joints with significantly fewer N-additions. Although likely heterozygous, individuals possessing these genetic changes may have less diverse B- and T-cell receptors that would particularly effect individuals prone to adaptive immune disorders, including autoimmunity.
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Troshchynsky
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: I
authors.initials: I
authors.lastname: Dzneladze
authors.affiliation: School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Sheng
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.
authors.forename: V
authors.initials: V
authors.lastname: Saridakis
authors.affiliation: Department of Biology, York University, Toronto, Ontario, Canada.|School of Kinesiology and Health Science, York University, Toronto, Ontario, Canada.|School of Biological Sciences, University of Canterbury, Christchurch, New Zealand.
authors.forename: G E
authors.initials: GE
authors.lastname: Wu
mesh_terms: D056704:Adaptive Immunity / Q000235:genetics; D004253:DNA Nucleotidylexotransferase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007135:Immunoglobulin Variable Region; D019169:Jurkat Cells; D008958:Models, Molecular; D009711:Nucleotides; D020641:Polymorphism, Single Nucleotide; D011948:Receptors, Antigen, T-Cell / Q000235:genetics; D060152:V(D)J Recombination
chemical_list: D007135:Immunoglobulin Variable Region; D009711:Nucleotides; D011948:Receptors, Antigen, T-Cell; D004253:DNA Nucleotidylexotransferase