ANALYSIS OF A REPLICATION INITIATION SEQUENCE FROM THE ADENOSINE-DEAMINASE REGION OF THE MOUSE GENOME

A 4-kb HindIII fragment that supported the efficient autonomous replic ation of plasmid vector pDY-, a replication-defective construct based on Epstein-Barr virus sequences, in human K562 cells was rescued from amplified double-minute chromosomes containing the murine adenosine de aminase locus. Polymerase chain reaction assays of size-fractionated n ascent strands demonstrated that replication initiation occurred withi n the same 1- to 2-kb region of this fragment in autonomously replicat ing plasmids containing the sequence in either orientation, in double- minute chromosomes, and in the single-copy locus at its normal chromos omal location. The complete sequence of this fragment was determined; it contains a 248-bp polypurine tract and consensus binding site seque nces for several putative transcription and replication factors.