ANALYSIS OF THE VPE SEQUENCES IN THE CAENORHABDITIS-ELEGANS VIT-2 PROMOTER WITH EXTRACHROMOSOMAL TANDEM ARRAY-CONTAINING TRANSGENIC STRAINS

The Caenorhabditis elegans vit genes, encoding vitellogenins, are abun dantly expressed in the adult hermaphrodite intestine. Two repeated el ements, vit promoter element 1 (VPE1 [TGTCAAT]) and VPE2 (CTGATAA), ha ve been identified in the 5' flanking DNA of each of the vit genes of C. elegans and Caenorhabditis byiggsae. These elements have previously been shown to be needed for correctly regulated expression of a vit-2 /vit-6 fusion gene in low-copy-number, integrated transgenes. Here we extend the analysis of the function of VPE1 and VPE2 by using transgen ic lines carrying large, extrachromosomal arrays of the test genes. Th e results validate the use of such arrays for transgenic analysis of g ene regulation in C. elegans, by confirming previous findings showing that the VPE1 at -45 and both VPE2s are sites of activation. Additiona l experiments now indicate that when the -45 VPE1 is inverted or repla ced by a VPE2, nearly total loss of promoter function results, suggest ing that the highly conserved -45 VPE1 plays a unique role in vit-2 pr omoter function. In contrast, single mutations eliminating the three u pstream VPE1s are without effect. However, in combination in double an d triple mutants, these upstream VPE1 mutations cause drastic reductio ns in expression levels. The -150 VPE2 can be replaced by a XhoI site (CTCGAG), and the -90 VPE2 can be eliminated, as long as the overlappi ng VPE1 is left intact, but when these two replacements are combined, activity is lost. Thus, the promoter must have at least one VPE2 and i t must have at least two VPE1s, one at -45 and one additional upstream element.