Worm Breeder's Gazette 8(2): 39
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.
We have previously reported the isolation of three distinct, non- homologous repetitive DNA families termed CeRep1, CeRep2, and CeRep3, respectively. The structure, organization and interrelationships of individual family members are being analyzed by DNA sequencing, electron microscopy, and cross-hybridization experiments. We have found that each family has a distinct and conserved structure with similarities to repetitive families that have been described for other organisms. CeRep1, present in 8-10 copies per genome, is organized with 450 bp terminal inverted repeats with variably-sized separating loop regions (500 bp to greater than 2.5 kb). The inverted repeats are 75-100% conserved and a 500 bp region in the loop is 80-90% conserved. This organizational pattern is reminiscent to Drosophila foldback elements, which are known to be transposable sequences. CeRep2 and CeRep3 are organized as 400-500 bp units that are present in about 15 and 100 copies in the genome, respectively. The elements are highly dispersed though extensive clusters have been detected. The CeRep3 element is extremely A-T-rich and has been found to share homology with known centromeric regions in yeast and other eukaryotes. To test for possible centromeric function, CeRep3 elements have been placed into yeast via an E. coli-yeast shuttle vector, and in addition the CeRep3 element has been microinjected into C. elegans. These experiments are in progress. With respect to transcriptional activity of these sequences, no RNA has been detected that is homologous to these families on Northern hybridizations.