Worm Breeder's Gazette 10(2): 107
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.
Like everyone else, we were convinced that worms should have as many homeobox containing genes as other organisms. Rather than continue with low stringency hybridizations with heterologous probes, we synthesized an oligonucleotide probe, using the worm codon bias, based on the most conserved sequence of known homeoboxes. This region, from amino acid 44 55, is the second helix of the helix- turn- helix region i.e. the putative DNA binding domain. Screening a genomic Southern with this probe showed seven strongly hybridizing bands that remained after high stringency washing. Numerous positive clones were then isolated from a genomic library. One of these clones, JM#L1001, was mapped by Alan Coulson to the left end of the X chromosome. Two other positive clones have not yet found a home in the genome. The first clone was sequenced and shown to contain a homeobox domain with 50% amino acid homology to Antennapedia. The 'homeobox' contains two introns based on estimates of splice-donor acceptor sites; one 47bp long between amino acids 21 and 22 and a second 48bp in length between amino acids 44 and 45. The homeobox domain is contained within a putative open reading frame of 190 amino acids. [See Figure 1] In RNA extracted from a total worm population,three different message sizes are apparent: a l.3kb species and two smaller species, approximately 800 and 600bp. The l.3kb message appears to be enriched in the poly A- fraction. The different species seems to be developmentally regulated but much more work is needed. We are now in the process of isolating the remaining homeobox containing genes. It will be interesting to see if the mec-3 gene will be isolated in the screen,since the Way-Chalfie sequence is only 69% homologous to our probe.