Terminal deoxynucleotidil transferase is a nuclear PKC substrate

Terminal deoxynucleotidyl transferase: the story of a misguided DNA polymerase

Nearly every DNA polymerase characterized to date exclusively catalyzes the incorporation of mononucleotides into a growing primer using a DNA or RNA template as a guide to direct each incorporation event. There is, however, one unique DNA polymerase designated terminal deoxynucleotidyl transferase that performs DNA synthesis using only single-stranded DNA as the nucleic acid substrate. In this chapter, we review the biological role of this enigmatic DNA polymerase and the biochemical mechanism for its ability to perform DNA synthesis in the absence of a templating strand. We compare and contrast the molecular events for template-independent DNA synthesis catalyzed by terminal deoxynucleotidyl transferase with other well-characterized DNA polymerases that perform template-dependent synthesis. This includes a quantitative inspection of how terminal deoxynucleotidyl transferase binds DNA and dNTP substrates, the possible involvement of a conformational change that precedes phosphoryl transfer, and kinetic steps that are associated with the release of products. These enzymatic steps are discussed within the context of the available structures of terminal deoxynucleotidyl transferase in the presence of DNA or nucleotide substrate. In addition, we discuss the ability of proteins involved in replication and recombination to regulate the activity of the terminal deoxynucleotidyl transferase. Finally, the biomedical role of this specialized DNA polymerase is discussed focusing on its involvement in cancer development and its use in biomedical applications such as labeling DNA for detecting apoptosis.

Phorbol ester synergizes the dimethyl sulfoxide-dependent programmed cell death through diacylglycerol increment

The regulation of cell proliferation or cell death by extracellular factors are the most intensely studied subjects in cell biology. Many conceptual problems remain to be clarified concerning the mechanisms that regulate the programmed cell death. In this work, we focus our attention on the possible role of protein kinase C activation during dimethyl sulfoxide (DMSO)-induced cell death. The present results suggest that the frequency of DMSO-dependent apoptosis of RPMI 8402 thymic lymphoma cells is increased by phorbol ester acetate supplementation. Enhancement of apoptosis can be abolished by cotreatment with the bisindolylmaleimide, a specific PKC inhibitor. The association between PMA and DMSO treatment provokes an early activation of an intracellular signaling mechanism that results, via sustained diacylglycerol elevation, in a possible long-term PKC activation.