Discrete size classes of monkey extrachromosomal circular DNA containing the L1 family of long interspersed nucleotide sequences are produced by a general non-sequence specific mechanism.

The L1 family of long interspersed nucleotide sequences (LINES) has recently been identified and characterized in the small polydisperse circular DNA (spc-DNA) populations of monkey (1), human (2) and mouse (3) cells. In monkey spc-DNA, the L1 (also known as Kpn I) family is present in discrete size classes (ranging from 300 to 6000 base pairs (bp)) which appear to be generated by non homologous recombination events within chromosomal elements. In this communication it is shown that different regions of the consensus L1 family are present at different frequencies in monkey spc-DNA (as they are in chromosomal DNA), that all regions of the family are present in extrachromosomal DNA, and that each region appears to be represented in an identical discrete spc-DNA size distribution. This size distribution reflects a non-sequence specific mechanism that generates spc-DNA size classes by chromosomal DNA recombination events that are in some way constrained to occur between sites separated by relatively defined lengths.