POLY(ADP-RIBOSE) POLYMERASE CAN BIND MELPHALAN DAMAGED DNA

As a means of identifying damage recognition proteins involved in repa ir of nitrogen mustard lesions in chronic lymphocytic leukemia, we per formed Southwestern analysis using a probe damaged with melphalan and protein extracts from chronic lymphocytic leukemia patients. We detect ed proteins with molecular weights of 116,000, 66,000, and 64,000 whic h bound the damaged probe with a higher specificity than the undamaged probe. The M(r) 66,000 and 64,000 proteins were determined to be degr adation products of the M(r) 116,000 protein. The M(r) 116,000 protein was identified as poly(ADP-ribose) polymerase. The use of methoxyamin e, an inhibitor of DNA strand breakage following depurination, signifi cantly reduced binding of the melphalan damaged probe to poly(ADP-ribo se) polymerase. Following depletion of poly(ADP-ribose) polymerase fro m the cell extracts, no other binding activity was discovered. Thus, p oly(ADP-ribose) polymerase is the only demonstrable protein in chronic lymphocytic leukemia cells which can bind to a DNA probe damaged with melphalan.