ANALYSIS OF 5'-TERMINI OF EARLY INTERMEDIATES OF OKAZAKI FRAGMENTS ACCUMULATED IN THYMOCYTES AFTER EMETINE TREATMENT OF MICE

Nascent Hg-DNA synthesized by the incorporation of Hg-dCTP in reversib ly permeable cells of murine thymocytes has been characterized earlier . Here we describe the analysis of 5' ends of oligonucleotides isolate d from thymocytes 48 hr after a single dose of emetine administration to mice. This small-molecular-weight population of nascent DNA shorter than Okazaki fragments was absent in control cells. More than 90% of the terminally P-32-labeled oligonucleotides carried a terminally phos phorylated RNA moiety at the 5' end, as demonstrated by alkaline hydro lysis, The size of the short nascent DNA fragments carrying RNA primer s ranged between 9 and 50 nucleotides with an average chain length of 15 nucleotides. These oligomers are regarded as the precursors of the Okazaki fragments.