Worm Breeder's Gazette 7(1): 52
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.
The presence of interspersed repetitive DNA sequences has been shown to be universal in all eukaryotic genomes that have been examined. In Caenorhabditis een shown that the genome is interspersed with short repeated sequences of an average length of 300 bp (Emmons et al., 1980). The function of these sequences, at present, is unknown. In addition, via hybridization of random genomic fragments back to the genome, it was shown that no single major family of repeated sequences exists, such as, for example, the 300,000 member 'Alu' family of primates (Emmons et al., 1979). The C. elegans genome seems to contain many small families with on the average 10 members or less, which are more easily studied. It is therefore possible to isolate and analyze all the members of a single repetitive family. By looking at the structure, organization, and possible expression of these sequences, it may be possible to ascertain their role in gene expression. In our studies a 450bp inverted repeat was isolated from a randomly cloned 10 kb BamHI restriction endonuclease fragment from the Bristol genome. via S1 nuclease digestion. This sequence was shown to hybridize to 14 other BamHI fragments in the genome. The fragments ranged in size from less than 0.7 kb to greater than 15 kb. All the fragments were shown to be conserved throughout the developmental stages as well as in the germ line. The inverted repeat isolated above hybridizes to Bergerac genomic DNA with the same repetition frequency and to the same size fragments as in Bristol. In addition, hybridization was shown to C. briggsae genomic DNA at three locations. It is noted, however, that the original 10 kb fragment carrying the inverted repeat is not detected in C. briggsae. The inverted repeat sequence was used to screen a Bristol genomic clone bank in the phage vector lambda1059 for the other hybridizing sequences, which constitute a family of repetitive sequences. Preliminary EM results indicate that very few of the hybrid phages isolated contain any secondary structure. This observation indicates that most of the family members exist as isolated repeats. In a case where secondary structure can be demonstrated, the size and structure of the inverted repeat is quite distinct from the 450bp inverted repeat used to define the family. Present experiments are concentrating on the genomic location of the repetitive sequences of the isolated family, that is, are they clustered or widely dispersed in the genome? Sequence analysis will soon be undertaken, as well as an examination of the possibility that members of this repetitive family may hybridize to members of other repetitive families. In addition, an attempt will be made to determine whether these sequences are transcribed.