ACTIVITY OF A C-ELEGANS GATA TRANSCRIPTION FACTOR, ELT-1, EXPRESSED IN YEAST

The GATA motif (WGATAR) is found in the promoter regions of numerous C aenorhabditis elegans genes, including two intestine-specific genes, v it-2 and ges-l, in which it has been shown to be required for promoter function. The protein ELT-1, encoded by a single-copy gene homologous to the GATA family of vertebrate transcription factors, is potentiall y capable of interacting with this element. In order to determine whet her ELT-1 is a transcriptional activator that recognizes this sequence , we have expressed it under the control of the GAL1 promoter in yeast . lacZ driven by the CYC1 promoter lacking an upstream activation sequ ence (UAS) but containing GATA sequences was used as a reporter. beta- Galactosidase was expressed upon induction only when GATA sequences we re present, and expression was increased dramatically by additional bi nding sites. Deletion analysis demonstrated that the C terminus, conta ining only one of the two zinc fingers, is sufficient for activation. In addition, the DNA-binding domain and two transactivation regions we re identified by fusing these isolated domains to previously defined d omains of heterologous transcription factors. While most single base a lterations in the GATA core sequence eliminated activity, an A to C ch ange in position four, creating a GATC core, was found to increase act ivity significantly. The deleted ELT-1 protein containing only the C-t erminal Zn finger was sufficient for activation in response to GATA, b ut both fingers were required for activation at GATC. A variety of sit es with non-optimal sequences surrounding the GATA core also were foun d to be excluded better by the protein containing both Zn fingers. Fur thermore, a fusion protein containing the entire ELT-1 DNA binding dom ain fused to the VP16 activation domain was found to have an even grea ter preference for the GATC core, as well as the optimal flanking base s. We conclude that, although ELT-1 having only its C-terminal finger is capable of activation in response to the WGATAR site, the presence of the upstream finger supplies additional base specificity. (C) 1995 Academic Press Limited