Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Saccharomyces cerevisiae, mutations in APN1, APN2 and either RAD1 or RAD10 genes are synthetic lethal. In fact, apn1 apn2 rad1 triple mutants can form microcolonies of approximately 300 cells. Expression of Nfo, the bacterial homologue of Apn1, suppresses the lethality. Turning off the expression of Nfo induces G(2)/M cell cycle arrest in an apn1 apn2 rad1 triple mutant. The activation of this checkpoint is RAD9 dependent and allows residual DNA repair. The Mus81/Mms4 complex was identified as one of these back-up repair activities. Furthermore, inactivation of Ntg1, Ntg2 and Ogg1 DNA N-glycosylase/AP lyases in the apn1 apn2 rad1 background delayed lethality, allowing the formation of minicolonies of approximately 10(5) cells. These results demonstrate that, under physiological conditions, endogenous DNA damage causes death in cells deficient in Apn1, Apn2 and Rad1/Rad10 proteins. We propose a model in which endogenous DNA abasic sites are converted into 3'-blocked single-strand breaks (SSBs) by DNA N-glycosylases/AP lyases. Therefore, we suggest that the essential and overlapping function of Apn1, Apn2, Rad1/Rad10 and Mus81/Mms4 is to repair 3'-blocked SSBs using their 3'-phosphodiesterase activity or their 3'-flap endonuclease activity, respectively.
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PMID:Endogenous DNA abasic sites cause cell death in the absence of Apn1, Apn2 and Rad1/Rad10 in Saccharomyces cerevisiae. 1203 96

Tyrosyl-DNA phosphodiesterase (TDP) cleaves the phosphodiester bond linking the active site tyrosine residue of topoisomerase I with the 3' terminus of DNA in topoisomerase I-DNA complexes which accumulate during treatment of cancer with camptothecin. In yeast, TDP mutation confers a 1000-fold hypersensitivity to camptothecin in the presence of an additional mutation of RAD9 gene [Pouliot, J.J., Yao, K.C., Robertson, C.A. & Nash, H.A. (1999) Science 286, 552-555]. Based on the recently solved crystal structure, human TDP belongs to a distinct class within the phospholipase D superfamily in spite of very low sequence homology [Interthal, H., Pouliot, J.J. & Champoux, J.J. (2001) Proc. Natl Acad. Sci. USA 98, 12009-12014, and Davies, D.R., Interthal, H., Champoux, J.J. & Hol, W.G.J. (2002) Structure 10, 237-248]. To understand the enzymatic mechanism of this novel enzyme, and to facilitate inhibitor screening of human TDP, we have expressed and purified recombinant human TDP variants carrying deletions of 1-39 or 1-174 amino acids. Furthermore, a continuous colorimetric assay in a 96-well format was also developed using p-nitrophenyl-thymidine-3'-phosphate as substrate. This assay system is able to detect enzymatic activity at enzyme concentrations as low as 15 nm. Purified recombinant human TDPNDelta39 cleaved p-nitrophenyl-thymidine-3'-phosphate with Km and kcat values of 211.14 +/- 23.83 micro m and 8.82 +/- 0.57 per min in the presence of Mn2+.
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PMID:Kinetic studies of human tyrosyl-DNA phosphodiesterase, an enzyme in the topoisomerase I DNA repair pathway. 1215 66