Three genes
ace-1,
ace-2 and
ace-3 encode three pharmacological classes of acetylcholinesterase (AChEs of class A, B and C respectively) in C. elegans (Johnson et al., 1988, Neuron 1, 165-173). The coding sequence and the genomic structure of
ace-1 have been determined (Arpagaus et al., 1994, J. Biol. Chem. 269, 9957-9965). The protein encoded by
ace-1 presents 42% of identity with human AChE. A null mutation in
ace-1 (allele
p1000) was originally characterized by a total absence of class A AChE (Johnson et al., 1981, Genomics 97, 261-279). We have found that this null mutation was due to an opal mutation TGG (W99) ---> TGA(Stop). This leads to a truncated peptide devoid of catalytic activity as well as a reduction of
ace-1 transcripts to only 10% of that in wild-type animals. This reduction is likely due to a destabilization of mRNA containing the non-sense message (Talesa et al., 1995, FEBS Lett. 357, 265-268). We have started to define the promoter region of
ace-1. A portion of
ace-1 mRNAs is transpliced by SL1. Two transcription starts were identified on the untranspliced RNA by 5' RACE experiments. Neither a TATA box nor a CAAT box was found in close proximity of these two sites. A 1.2 kb fragment of the 5' region was tested for functional promoter activity by CAT assay in mouse fibroblasts 10T1/2. Preliminary results show that this region as well as a 5' deleted fragment of 795 bp exhibited promoter activity. Thus
ace-1 promoter is recognized by the transcription apparatus of mouse cells (Culetto et al., 1995, WBG 13-5, 43). In order to select potential regulatory sequences in 5' region of
ace-1, we have cloned
ace-1 gene in C. briggsae for comparison. We will report recent results of this study.