Early growth response gene-1 plays a pivotal role in down-regulation of a cohort of genes in uterine leiomyoma.

Microarray studies have identified many genes that are down-regulated in uterine leiomyoma compared with myometrium, including early growth response gene-1 (EGR1). However, the mechanisms underlying coordinated down-regulation of this gene cohort remain unknown. To address the transcriptional role of EGR1 in leiomyoma, EGR1 binding to promoter sequences on target genes was assessed by chromatin immunoprecipitation (ChIP) assay in leiomyoma tissues and myometrium-derived KW cells. Computer analysis demonstrated that 50 out of 135 genes listed as down-regulated in array reports possessed potential binding sites for EGR1 within 1 kb promoter sequence. ChIP assay was performed for a random selection of 13 genes possessing potential binding sites for EGR1 (Group A), 3 genes known as EGR1 targets in other tissues (Group B), and 4 control genes. Decreased EGR1 bindings were significant for 11 out of 16 genes (Group A+B) in leiomyoma tissues compared with myometrium, and mRNA levels in tissue samples were actually decreased for 7 out of the 11 genes. ChIP analyses performed on KW cells showed induction of EGR1 binding to the promoter region of all genes except one Group A+B gene, but for none of the control genes. These results indicate that EGR1 is a key player in coordinated down-regulation of genes in leiomyoma. Application of ChIP-quantitative PCR assay with the aid of computer-assisted analysis of genome databases appears useful for the comprehensive interpretation of array data.