DNA-PROTEIN INTERACTIONS IN THE CAENORHABDITIS-ELEGANS EMBRYO - OOCYTE AND EMBRYONIC FACTORS THAT BIND TO THE PROMOTER OF THE GUT-SPECIFIC GES-1 GENE

We describe an experimental system in which to investigate DNA-protein interactions in the early Caenorhabditis elegans embryo. A homogeneou s population of developmentally blocked mid-proliferation stage embryo s can be produced by exposure to the deoxynucleotide analog fluorodeox yuridine. These blocked embryos remain viable for days and express a n umber of biochemical markers of early differentiation, for example, gu t granules, the gut esterase ges-1, and two regulatory genes, mab-5 an d hlh-1. Using the techniques of gel mobility shift and DNase I footpr inting, we show that nuclear extracts prepared from these embryos cont ain factors that bind to the 5'-promoter sequences of the C. elegans g ut-specific ges-1 gene. In particular, we examine a putative gut ''act ivator'' region, which was previously identified by deletion-transform ation analysis and which contains two copies of a consensus GATA-facto r binding sequence. Factors that bind to double-stranded oligonucleoti des containing the ges-1 GATA sequences are present predominantly in n uclear extracts of embryos but are found neither in cytoplasmic nor in nuclear extracts of unfertilized oocytes. Two proteins, of 43 and 60 kDa, can be uv-crosslinked to double-stranded oligonucleotides contain ing the ges-1 GATA sequences. The sizes of these proteins correspond t o the sizes expected for the elt-1 protein and for the skn-1 protein, two regulatory factors present in early C. elegans embryos and possibl e candidates for ges-1 control. However, we show that homozygous defic iency embryos (mDf7/mDf7 embryos and eDf19/eDf19 embryos, both of whic h lack the elt-1 gene, and nDf41/nDf41 embryos, which have no skn-1 ge ne), still express the ges-1 esterase. We conclude that neither the el t-1 gene nor the skn-1 gene is necessary zygotically for ges-1 express ion. We suggest that neither the elt-1 protein nor the skn-1 protein i nteracts directly with the ges-1 gene and that the observed binding pr oteins must correspond to products of other genes. More generally, the present experimental system should allow the biochemical study of any gene expressed during early C. elegans embryogenesis. (C) 1994 Academ ic Press, Inc.