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Nat Immunol. 2002 May;3(5):457-62. Epub 2002 Apr 8.

Distinct and opposite diversifying activities of terminal transferase splice variants.

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Division of Developmental and Clinical Immunology, Department of Microbiology, The University of Alabama at Birmingham, 35294, USA.


The short splice variant of mouse terminal deoxynucleotidyl transferase (TdTS) catalyzes the addition of nontemplated nucleotides (N addition) at the coding joins of B cell and T cell antigen receptor genes. However, the activity and function of the long isoform of TdT (TdTL) have not been determined. We show here, in vitro and in vivo, that TdTL is a 3'-->5' exonuclease that catalyzes the deletion of nucleotides at coding joins. These findings suggest that the two TdT isoforms may act in concert to preserve the integrity of the variable region of antigen receptors while generating diversity.

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