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.

Sequence Analysis of the Transposable Element Tc2

Vivian R. Ruvolo and Alexandra Levitt

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 
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.