Worm Breeder's Gazette 11(5): 35
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.
In the last few years our group has been studying the large scale organization of repetitive DNA sequences. We are characterizing six repetitive DNA families interspersed in the genome of C. elegans: RcA1, RcD1, Rc35, RcC9, RcS5 and RcB1. We presented in CSH 1989 the physical distribution of our repeated elements in the genome. Some of these families (RcD1, Rc35, RcC9, see also La Volpe et al. (1988) Nucl. Acids Res. 16, 82138231 ) are characterized by the presence of short tandemly repeated modules (satellite-like repetitive DNA). We compared the sequence of three elements belonging to the RcA1 family (Copy number: 161) localized on chromosomes I, II and V respectively; each member is 118 bp in length and the core region of 46bp is perfectly conserved between the three. The elements of the RcD1 family (present at 138 loci in the genome) are characterized by tandem repetitions of an extremely conserved 15bp unit. The Rc35 is another satellite-like family localized at 76 loci; the tandem repeated module is 35bp long. The RcC9 family described in La Volpe et al. (1988) has the basic tandemly repeated unit of 10bp (and the same consensus of the Heat-Shock Element) and is present at 84 positions on C. elegans genome. An element belonging to the RcB1 family (copy number 57) is characterized by the presence of direct terminal repeats of 64 bp. We observed that, although they are present along all the chromosomes, these families are not distributed completely randomly, but there are some regions of accumulation of elements belonging to different repetitive families, some of which we analyzed in detail by sequencing. There is an inverse correlation between the presence of repetitive regions along the chromosomes and the frequency of recombination, that recalls the repression of legitimate recombination near the centromeres of Drosophila and Schizosaccharomyces pombe.