There are two heptamers repeated multiple times upstream of the C. enin genes. In order to obtain evidence for or against the functional importance of these heptamers we have investigated their evolutionary stability. We sequenced the homologous promoters from C. briggsae and the only C. enin promoter remaining unsequenced
vit-3. This brings the total number of nematode vitellogenin promoters sequenced to eleven. The data are shown schematically in the Figure. Box 1 TGTCAAT, is shown as rectangles; Box 2 CTGATAA is shown as ovals. In general the heptamers have beer very highly conserved while the sequences between them have diverged considerably. In particular there has been strong conservation of the Box 1 heptamers centered at -45 ( just upstream of the TArA box)those at -180 (which we have suggested may be at the 5' border of the promoter regions) and at least one Box 1 between -45 and -180. In each case the locations and sequences of at least these Box 1 heptamers and at least one Box 2 heptamer per promoter have been conserved. This data strongly supports the hypothesis that Box 1 and Box 2 are involved in vit promoter function. We are initiating experiments to determine the relationship between the two heptamers and the three modes of regulation: sex stage and tissue. {Figure 1} We have noted previously the presence of Box 2 in the vertebrate vitellogenin promoters. Klein-Hitpass et al. (Cell 46 1053) have tested the idea that this heptamer plays a role in Xenopus vitellogenin gene induction by estrogen in a transient expression assay using a human mammary cell line. They present evidence that it is a binding site for an activator protein required for estrogen induction but not the site for estrogen receptor itself. They name it the 'elegans box'. Does this mean that the regulatory protein that binds to this sequence in the C. e is also present in human mammary cells?