Analysis of 5'-ends of short DNA fragments excreted by phytohemagglutinin stimulated lymphocytes.

Human peripheral blood lymphocytes were stimulated with phytohemagglutinin and the excreted DNA was isolated from the medium after four days of incubation of cells. The excreted DNA was labeled at the 5'-end with [gamma-32P]ATP and polynucleotide kinase. Analysis of the end-labeled material revealed a size distribution with a chain length of 6 - 60 nucleotides. These short DNA fragments did not contain ribo-nucleotides at their 5'-termini. P1 nuclease digestion did not release specific deoxyribonucleoside monophosphates from the 5'-end of the excreted DNA fragments. These results point to the non-specific degradation of DNA excreted by stimulated lymphocytes.