Genome-wide analysis of Bkm sequences (GATA repeats): predominant association with sex chromosomes and potential role in higher order chromatin organization and function

MOTIVATION: Bkm (Banded krait minor) satellite DNA sequences (GATA repeats) have been shown to be associated with the sex determining chromosomes of various eukaryotes and have been implicated in the evolution and differentiation of sex chromosomes in snakes. The objective of the study is to analyze the GATA repeats of human genome specifically, the Y-chromosome, and other model organisms to understand the possible function and potential role in higher order chromatin organization. RESULTS: Our extensive analysis of GATA repeats in the prokaryotic and eukaryotic genomes, which have been completely sequenced so far, has revealed that GATA repeats are absent in prokaryotes and have been gradually accumulated in higher organisms during the course of evolution. In human, the Y-chromosome has the highest GATA repeat density, which predominantly exists in the Yq centromeric region. Generally, occurrence of repeats in the genomes decreases steadily as the length of the repeat increases. In contrast, we report, that the occurrence of GATA repeats increases as the length of the repeat increases from six tandem repeats onwards and peaks at (GATA)(10-12). This has not been observed with any other simple repeat. Distribution of (GATA)(10-12) along the chromosome and their close proximity to Matrix Associated Regions (GATA-MAR) suggests that it may be demarking chromatin domains for a coordinated expression of genes residing in these domains.