| Autor: |
Samejima, K, Svingen, P A, Basi, G S, Kottke, T, Mesner, P W, Stewart, L, Durrieu, F, Poirier, G G, Alnemri, E S, Champoux, J J, Kaufmann, S H, Earnshaw, W C |
| Zdroj: |
Journal of Biological Chemistry; February 1999, Vol. 274 Issue: 7 p4335-40, 6p |
| Abstrakt: |
Previous studies have demonstrated that topoisomerase I is cleaved late during apoptosis, but have not identified the proteases responsible or examined the functional consequences of this cleavage. Here, we have shown that treatment of purified topoisomerase I with caspase-3 resulted in cleavage at DDVD146 downward arrowY and EEED170 downward arrowG, whereas treatment with caspase-6 resulted in cleavage at PEDD123 downward arrowG and EEED170 downward arrowG. After treatment of Jurkat T lymphocytic leukemia cells with anti-Fas antibody or A549 lung cancer cells with topotecan, etoposide, or paclitaxel, the topoisomerase I fragment comigrated with the product that resulted from caspase-3 cleavage at DDVD146 downward arrowY. In contrast, two discrete topoisomerase I fragments that appeared to result from cleavage at DDVD146 downward arrowY and EEED170 downward arrowG were observed after treatment of MDA-MB-468 breast cancer cells with paclitaxel. Topoisomerase I cleavage did not occur in apoptotic MCF-7 cells, which lack caspase-3. Cell fractionation and band depletion studies with the topoisomerase I poison topotecan revealed that the topoisomerase I fragment remains in proximity to the chromatin and retains the ability to bind to and cleave DNA. These observations indicate that topoisomerase I is a substrate of caspase-3 and possibly caspase-6, but is cleaved at sequences that differ from those ordinarily preferred by these enzymes, thereby providing a potential explanation why topoisomerase I cleavage lags behind that of classical caspase substrates such as poly(ADP-ribose) polymerase and lamin B1. |
| Databáze: |
Supplemental Index |
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