DNA-NUCLEASE ACTIVITY OF THE SINGLE-CHAIN RIBOSOME-INACTIVATING PROTEINS DIANTHIN-30, SAPORIN-6 AND GELONIN

The single-chain ribosome-inactivating proteins (sc-RIPs) from plant o rigin are antiviral and antiproliferative agents employed in the prepa ration of immunotoxins, Similarly to the A-chains of ricin, sc-RIPs ac t as rRNA N-glycosidases. We demonstrate here that dianthin 30, sapori n 6 and gelonin exert a specific nuclease activity on supercoiled DNA. Four specific sites of cleavage introduced by dianthin 30 and by sapo rin 6 and two specific sites of cleavage introduced by gelonin have be en identified and mapped in pBR322.