Nuclease activity associated with the Ustilago maydis virus induced killer proteins

An in vitro nuclease activity was found to be associated with the purified killer proteins of Ustilago maydis. The proteins are effective against single stranded RNA, single and double stranded DNA. Endonucleolytic activity was confirmed by cleavage of circular molecules of 0x174 and PM2. Double stranded RNA did not appear to serve as a substrate.