Worm Breeder's Gazette 11(4): 31
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
A transposed copy of the mobile element Tc2 has been cloned and sequenced from the Bergerac/Bristol recombinant strain RW7406. The element is 2074 base pairs in length and contains both inverted and direct repeats at each end. The termini of the element consist of a 24 base pair perfect inverted repeat, and there is a 60-80 base pair AT-rich sequence approximately 150 base pairs in from each end. Between the ends of the element and the AT-rich region is a degenerate direct repeat that consists of overlapping tandem repeats based on a 10 base pair motif. In addition, our analysis suggests that Tc2 may have the capacity to code for a transposase protein and/or for regulatory functions. The element contains 9 potential open reading frames of 75 codons or longer, six on one strand and three on the other. We have defined the ends of the Tc2 element by examining the sequence of the corresponding 'empty site' fragment from the Bergerac strain. Our analysis indicates that this copy of the element has transposed into a highly repetitive chromosomal region. The transposon's insertion site lies at the beginning of a 120 base pair triple tandem repeat which is followed by two shorter multiple repeats (of fourteen and six copies respectively), which resemble the satellite sequences of other eukaryotes. Like Tc1, the Tc2 element is flanked by a two-base pair (AT) target site duplication. Satellite DNA has not previously been reported in C. elegans. In other eukaryotes, satellite sequences are typically found near centromeres. The chromosomes of C. elegans, however, are holocentric, and the distribution of these sequences in the genome if they have a structural function may be novel. Surprisingly, an open reading frame analysis of the repeat region suggests that it may contain one or more transcription units. We are currently analyzing polymorphic copies of Tc2; studying Tc2 transcripts; and determining the number and distribution of satellite- like sequences in the worm genome.