TdT catalyses the addition of nucleotides to the 3' terminus of a DNA molecule. Unlike most DNA polymerases, it does not require a template. The preferred substrate of this enzyme is a 3'-overhang, but it can also add nucleotides to blunt or recessed 3' ends. Cobalt is a necessary cofactor, however the enzyme catalyzes reaction upon Mg and Mn administration in vitro.
Terminal transferase has applications in molecular biology. It can be used in RACE to add nucleotides that can then be used as a template for a primer in subsequent PCR. It can also be used to add nucleotides labeled with radioactiveisotopes, for example in the TUNEL assay (Terminal deoxynucleotidyl transferase dUTP Nick End Labeling) for the demonstration of apoptosis (which is marked, in part, by fragmented DNA). Also used in the immunofluorescence assay for the diagnosis of acute lymphoblastic leukemia.
In immunohistochemistry, antibodies to TdT can be used to demonstrate the presence of immature T and B cells and multipotent haematopoietic stem cells, which possess the antigen, while mature lymphoid cells are always TdT-negative. While TdT-positive cells are found in small numbers in healthy lymph nodes and tonsils, the malignant cells of acute lymphoblastic leukaemia are also TdT-positive, and the antibody can, therefore, be used as part of a panel to diagnose this disease and to distinguish it from, for example, small cell tumours of childhood.
^Yang-Feng TL, Landau NR, Baltimore D, Francke U (1986). "The terminal deoxynucleotidyltransferase gene is located on human chromosome 10 (10q23-q24) and on mouse chromosome 19". Cytogenet. Cell Genet.43 (3-4): 121–6. doi:10.1159/000132309. PMID3467897.
^Hardy, Richard (2008). "Chapter 7: B Lymphocyte Development and Biology". In Paul, William. Fundamental Immunology (Book|format= requires |url= (help)) (6th ed.). Philadelphia: Lippincott Williams & Wilkins. pp. 237–269. ISBN0-7817-6519-6.
^Faber J, Kantarjian H, Roberts MW, Keating M, Freireich E, Albitar M (January 2000). "Terminal deoxynucleotidyl transferase-negative acute lymphoblastic leukemia". Arch. Pathol. Lab. Med.124 (1): 92–7. PMID10629138.
^Leong, Anthony S-Y; Cooper, Kumarason; Leong, F Joel W-M (2003). Manual of Diagnostic Cytology (2 ed.). Greenwich Medical Media, Ltd. pp. 413–414. ISBN1-84110-100-1.
O'Malley DP, Orazi A (2006). "Terminal deoxynucleotidyl transferase-positive cells in spleen, appendix and branchial cleft cysts in pediatric patients.". Haematologica91 (8): 1139–40. PMID16885057.
Yamashita N, Shimazaki N, Ibe S, et al. (2001). "Terminal deoxynucleotidyltransferase directly interacts with a novel nuclear protein that is homologous to p65.". Genes Cells6 (7): 641–52. doi:10.1046/j.1365-2443.2001.00449.x. PMID11473582.
Maezawa S, Hayano T, Koiwai K, et al. (2008). "Bood POZ containing gene type 2 is a human counterpart of yeast Btb3p and promotes the degradation of terminal deoxynucleotidyltransferase.". Genes Cells13 (5): 439–57. doi:10.1111/j.1365-2443.2008.01179.x. PMID18429817.
Dworzak MN, Fritsch G, Fröschl G, et al. (1998). "Four-color flow cytometric investigation of terminal deoxynucleotidyl transferase-positive lymphoid precursors in pediatric bone marrow: CD79a expression precedes CD19 in early B-cell ontogeny.". Blood92 (9): 3203–9. PMID9787156.
Fujita K, Shimazaki N, Ohta Y, et al. (2003). "Terminal deoxynucleotidyltransferase forms a ternary complex with a novel chromatin remodeling protein with 82 kDa and core histone.". Genes Cells8 (6): 559–71. doi:10.1046/j.1365-2443.2003.00656.x. PMID12786946.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library.". Gene200 (1-2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.