Is terminal deoxynucleotidyl transferase an intracellular mutagen?

Terminal deoxynucleotidil transferase is a nuclear PKC substrate

Protein phosphorylation is the regulatory mechanism of many cellular events in response to changes in metabolic activity and environmental conditions. Seeing that PKC and TdT levels in cells are both regulated by PMA, we sought particularly intriguing to investigate TdT phosphorylation in vivo, utilizing KM-3 cells, a TdT-positive human pre-B cell line treated with PMA and in vitro, employing purified PKC and human recombinant TdT. Our data show that TdT is a substrate for PKC activity, suggesting that TdT phosphorylation could play a key role in the pathway affecting the control of gene transcription and protein synthesis during lymphoid cells differentiation.

Intracellular localization of terminal transferase during the cell cycle

Changes in the localization of terminal transferase during the cell cycle in random cultures of human pre-T leukemia line RPMI-8402 were examined by light and electron microscopy on immunoperoxidase-stained preparations. Paraformaldehyde-fixed and saponin-permeabilized human cells were used with a monoclonal anti-human terminal deoxynucleotidyl transferase (TdT) primary reagent to demonstrate changes in enzyme distribution occurring between interphase and mitosis. Nuclear localization is found uniformly during interphase. At metaphase, however, the majority of TdT staining appears randomly distributed in the cytoplasm and traces of TdT staining remain associated with mitotic chromatin. At later phases, when the daughter cells are forming, the enzyme again appears to be restricted to the new nuclear structure.

Association between nuclear matrix and terminal transferase: an electron microscope immunocytochemical analysis

Nuclear matrix extracted from KM-3, a human pre-B leukemia cell line, appears to have a site of linkage for terminal deoxynucleotidyl transferase (TdT). The immunocytochemical analysis of the distribution of TdT using a rabbit polyclonal antibody which recognizes human terminal transferase, shows that the nuclear framework of these cells contains sites of immunoreactivity that appear uniformly distributed on the matrix fibres, while the nucleolar region is unreactive. This evidence points out the possibility that TdT could reside in the proteinaceous scaffold of the nucleus defined as nuclear matrix, thus strengthening the evidence for the metabolic and regulatory roles ascribed to this nuclear framework.