Worm Breeder's Gazette 13(1): 61 (October 1, 1993)
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.
Ges-1 ,a gut-specific esterase first expressed at the 4-8E stage of development is a convenient marker gene to study early intestine development in C. elegans. We are interested in the factors that bind to the control region of the ges-1 gene to bring about its regulation. Footprinting and band-shift experiments using nuclear extracts from embryos (V. Stroeher et al., submitted) have identified a number of protein factors that bind to a region of the ges-1 gene 1.0 -1.3 kB upstream of the ATG. Of particular interest is a region that contains two WGATAR motifs similar to the VPE2 elements identified in the C. elegans vitellogenin genes, which are also expressed in a gut specific manner (MacMorris et al, 1992. Mol. Cell Biol. 12, 1652-1662). Egan et al. (see abstracts of the 1993 International C. elegans meeting) have shown that these GATA motifs are important for the gut-specific expression of ges-1 .We therefore used multimerized GATA-containing double stranded oligonucleotides to screen approximately 300,000 plaques from a C. elegans, mixed stage cDNA expression library ( Okkema et a/., WBG V ol12 ,ii).One clone was identified on the criteria of DNA-protein binding. This clone was then used to isolate a number of apparently close to full length cDNA clones from an independent C. elegans mixed stage cDNA library. The full length cDNA is 1597 nucleotides in length, is SL1 trans-spliced and contains a putative open reading frame of 433 amino acids in length, ie. encoding a protein of approximately 47,000Mr. Sequence analysis has shown the protein to be similar to GATA-factors isolated from a diverse range of species including elt-1 (C. elegans, Spieth et al., 1991. Mol. Cell Biol. 11, 4651-4659), GATA-4 (Mice, Arceci et al., 1993. Mol. Cell Biol. 13, 2235-2246), GATA-3 (Xenopus, Zon etal., 1991. Proc. Natl. Acad. Sci. USA. 88, 10642-10646), GATA-2 (humans, Lee et al., 1991. J. Biol. Chem. 266, 16188-16192) and GATA-1 (chicken, Evans and Felsenfeld, 1989. Cell 58,877-885). The new GATA factor contains two putative zinc-fingers as shown below. The C-terminal zinc-finger shows a similarity of 76%-80% when compared to the C-terminal zinc-fingers of the GATA factors listed above. However, the N-terminal zinc-finger shows a lower degree of similarity when compared to all other known GATA-factors ie. it has the sequence C-V-K-C-N(16)-C-V-N-C instead of the conserved motif C-X-N-C-N(17)-C-N-X-C. Furthermore the inter-finger distance is different from other GATA-factors. Thus we do not know if the protein has two zinc-fingers or one zinc-finger and a pseudo zinc-finger. It has been shown with the other GATA-factors that the C-terminal finger is much more important for DNA binding. For example Ormichinski et al. (1993, Proc. Natl. Acad. Sci. USA. 90, 1676-1680) showed the C-terminal zinc-finger of Chick GATA-1 was necessary for sequence specific DNA-protein interaction.
The important question is whether the new gene is involved in regulating ges-1 and we hope to approach this via Tc1 insertion mutants and studying expression patterns. We now have genomic clones but they have yet to be positioned onto the C. elegans physical map.