INDUCTION OF UBIQUITIN-CONJUGATING ENZYME-ACTIVITY FOR DEGRADATION OFTOPOISOMERASE II-ALPHA DURING ADENOVIRUS E1A-INDUCED APOPTOSIS

Topoisomerase (tops) II alpha is degraded via polyubiquitination durin g adenovirus E1A-induced apoptosis in MA1 cells, a derivative of the h uman epidermoid carcinoma cell line KB. Topo II alpha ubiquitination a ctivity in MA1 cells increased nearly 10 fold after induction of E1A i n response to dexamethasone. To identify a topo II alpha ubiquitinatio n factor(s), the S100 fractions prepared from apoptosis-induced (42 h) and uninduced (0 h) MA1 cells were first fractionated by ubiquitin-Se pharose columns. The ubiquitination activity induced by E1A was predom inantly eluted with 20 mM AMP. Further fractionation of the AMP eluate s on Resource-Q columns and the thiolester formation of the proteins r esolved by electrophoresis with biotinylated ubiquitin revealed that a species of E2 isozyme recovered in the QFT2 fraction increased marked ly in MA1 cells after E1A expression. These results indicate that a ub iquitination factor(s) specific to topo II alpha is induced during E1A -induced apoptosis in MA1 cells. (C) 1997 Academic Press.