Topoisomerases are enzymes with both nuclease and ligase activity. This enzyme is the extracellular nuclease of Staphylococcus aureus. They termed the nuclease enzyme RISC. Mild formaldehyde crosslinking followed by nuclease digestion has been used to shear the chromatin. Native ChIP (NChIP) uses native chromatin sheared by micrococcal nuclease digestion. SLBP also stabilizes histone mRNAs during S phase by blocking degradation by the 3'hExo nuclease. The cells are then lysed and digested with micrococcal nuclease. One such nuclease is Mre11 complexed with Rad50. The first type of enzyme was called a "methylase" and the other a "restriction nuclease". Cdk1 phosphorylates the nuclease Sae2, allowing resection to initiate. Modified aptamers ideally exhibit and high binding affinity, specificity, and nuclease resistance. Moreover, the use of restriction enzymes such as the zinc-finger nuclease (ZFN) is being studied. The protein consists of a recognition lobe (REC) and a nuclease lobe (NUC). Fragments are made are made blunt ended using S1 nuclease. It also protects the T-strand from nuclease attack.