elt-1, an embryonically expressed Caenorhabditis elegans gene homologous to the GATA transcription factor family

Abstract

The short, asymmetrical DNA sequence to which the vertebrate GATA family of transcription factors binds is present in some Caenorhabditis elegans gene regulatory regions: it is required for activation of the vitellogenin genes and is also found just 5' of the TATA boxes of tra-2 and the msp genes. In vertebrates GATA-1 is specific to erythroid lineages, whereas GATA-2 and GATA-3 are present in multiple tissues. In an effort to identify the trans-acting factors that may recognize this sequence element in C. elegans, we used a degenerate oligonucleotide to clone a C. elegans homolog to this gene. We call this gene elt-1 (erythrocytelike transcription factor). It is single copy and specifies a 1.75-kb mRNA that is present predominantly, if not exclusively, in embryos. The region of elt-1 encoding two zinc fingers is remarkably similar to the DNA-binding domain of the vertebrate GATA-binding proteins. However, outside of the DNA-binding domains the amino acid sequences are quite divergent. Nevertheless, introns are located at identical or nearly identical positions in elt-1 and the mouse GATA-1 gene. In addition, elt-1 mRNA is trans-spliced to the 22-base untranslated leader, SL1. The DNA upstream of the elt-1 TATA box contains eight copies of the GATA recognition sequence within the first 300 bp, suggesting that elt-1 may be autogenously regulated. Our results suggest that the specialized role of GATA-1 in erythroid gene expression was derived after separation of the nematodes and the line that led to the vertebrates, since C. elegans lacks an erythroid lineage.