Nuclease activity in HAMLET induced DNA fragmentation.

<p><i>A</i>) HAMLET was mixed with either pneumococcal chromosomal DNA or chromosomal DNA from Jurkat cells in the presence of both 1 mM each of Ca²⁺ and Mg²⁺ and the mixture was incubated for 1 hour and digestion was examined by gel electrophoresis. Bovine pancreas DNAse I was used as a positive control for DNA cleavage. HAMLET was unable to cleave either DNA preparation. (<i>B</i>) <i>S. pneumoniae</i> R6 (WT) and the isogenic strains 577 (<b>Δ</b><i>endA</i>), 641 (<b>Δ</b><i>exoA</i>) and 642 (<b>Δ</b><i>endA, </i><b>Δ</b><i>exoA</i>) were incubated with 100 or 200 µg/ml of HAMLET for 2 h and high molecular weight DNA fragmentation was examined. All strains displayed an accumulation of HMW DNA fragments.