Genomic arrangement of repeated PS700 elements in the nematode Panagrellus silusiae

When genomic DNA from the free-living nematode Panagrellus silusiae is digested with the restriction endonuclease BamHI and separated by electrophoresis, a band in the 700 base pair size range is evident after ethidium bromide staining. One of the 0.7-kilobase fragments (PS700-1) was characterized and found to be a member of a moderately repetitive DNA family (T. Warren and J.J. Pasternak. 1988. Nucleic Acids Res. 16: 10,833-10,847). In the current study, DNA sequence analyses of three independently isolated copies of the PS700 DNA family showed the same nucleotide sequence and greater than 98% similarity to PS700-1. Four EMBL-4 bacteriophage clones were isolated from a Panagrellus genomic DNA library with PS700-1 as the probe and were analyzed by restriction endonuclease site mapping and Southern blot DNA hybridization. These clones contain 31 copies of the PS700 DNA family. In each case, the units are arranged in head-to-tail arrays. One of the EMBL-4 clones contains copies of a novel variant of the PS700 elements. The maintenance of both nucleotide sequence and restriction endonuclease restriction site homogeneity among members of the dispersed PS700 DNA family may denote a functional role for these sequences.