Occurrence of the (GATA)n sequences in vertebrate and invertebrate genomes.

Clusters of the tetranucleotide GATA are found throughout the mouse genome with a major concentration on the Y chromosome. In Drosophila melanogaster, by contrast, they have a significant concentration on the X chromosome. Largely on the basis of these sex chromosomal concentrations and on their transcriptional activity in the mouse, these simple sequence tracts have been thought to be important in sex-determining and X inactivation mechanisms in both vertebrates and invertebrates. In every tested case the interpretations of the data have been difficult and sometimes the data themselves have been conflicting. We demonstrate in this paper that significant tracts of (GATA)n are totally absent from ovine and bovine genomes and point out that none of the major clusters of these repetitive sequences are near any of the sex-determining genes in D. melanogaster. We conclude therefore that (GATA)n sequences are not conserved over long evolutionary time periods as has previously been thought. Their absence from at least two mammalian genomes places severe constraints on their possible functions.