Worm Breeder's Gazette 16(4): 21 (October 1, 2000)
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.
Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Denver, CO 80262
Several years ago we became interested in the 3’ splice site recognition protein, U2AF. The large subunit of this protein is encoded by the uaf-1 gene, which we cloned and sequenced from C. briggsae because we were unable to obtain the C. elegans genomic clone. Recently, however, the genome consortium was finally able to clone and sequence the region from C. elegans (Y92C3B.a) and the comparison with the C. briggsae sequence is quite surprising. Both uaf-1 genes are downstream genes in an operon with a rab homolog. However, the uaf-1 gene is almost 6-fold larger in C. elegans (13.8 kb) than it is in C. briggsae (2.4 kb), principally because it contains two extra introns, and virtually all the introns present in C. briggsae are dramatically bigger in C. elegans. This is in sharp contrast to most previous comparisons of orthologous genes between these two species, where exons have been found to be very highly conserved while introns diverged at the sequence level but remained similar in size. The figure shows a comparison of intron and exon lengths for the two species. We don’t have any idea why there has been such a massive set of changes in this region of the genome since the separation of C. elegans and C. briggsae, nor do we know which genomic arrangement represents the ancestral state. Preliminary analysis of the C. elegans introns indicates they are composed largely of repetitive DNA, repeats of which also appear elsewhere in the genome. These observations do imply that different regions of the same genome can undergo very different degrees of change over the same period of time.