SYNTHESIS AND MATURATION OF PHAGE P22 DNA .I. IDENTIFICATION OF INTERMEDIATES

[摘要] Two intermediates in the synthesis and maturation of phage P22 DNA were identified by sedimentation of lysozyme-detergent lysates of induced lysogens or infected cells through sucrose density-gradients. Intermediate I contains most of the radioactivity incorporated during a short pulse of [3H] thymidine; it sediments at a rate in excess of 1000 s. If a short pulse of [3H] thymine is chased with unlabeled thymidine, labeled DNA appears in intermediate n, which has a sedimentation rate 1.2-1.7 times that of mature phage DNA in both neutral and alkaline sucrose gradients; 32P-labeled parental phage DNA appears 1st in intermediate I and later in intermediate II. The transfer of labeled DNA from intermediate I into intermediate II appears to be a late phage function; progeny phage heads contain DNA apparently derived from the intermediates. It is suggested that intermediate I represents the replicating phage DNA specifically attached to some other constituent of the induced or infected cell, and that intermediate II contains polynucleotide chains longer than those of the mature phage DNA.