The transcriptional repressor ICER binds to multiple loci throughout the genome

The events culminating in ovulation are controlled by the cyclical actions of hormones such as Follical Stimulating Hormone (FSH) and Luteinizing Hormone (LH). The secondary messenger, cyclic AMP (cAMP) conveys the intracellular activity of these hormones. It is well established that a family of transcription factors facilitate cAMP mediated gene expression, yet it remains unknown how these factors directly affect ovulation. One of these factors, Inducible cAMP Early Repressor (ICER) has been implicated in the transcriptional regulation of cAMP inducible genes during folliculogenesis and ovulation. In order to better determine the role of ICER in ovarian function we have identified novel targets using a genome-wide approach. Using a modification of the chromatin immunoprecipitation (ChIP) assay we directly cloned and sequenced the immunoprecipitated ICER-associated DNAs from an immortalized mouse granulose cell line (GRMO2). The analysis of the immunoprecipitated DNA fragments has revealed that ICER's binding to DNA has the following distribution; 16% within the promoter region, 31% within an intron, 14% were not within a gene, 6% were within 20 kb of a promoter and 3% were within the 3′ end of genes.