cis-regulatory region analysis using BEARR.

Genome-wide studies are fast becoming the norm, partly fueled by the availability of genome sequences and the feasibility of high-throughput experimental platforms, e.g., microarrays. An important aspect in any genome-wide studies is determination of regulatory relationships, believed to be primarily transacted through transcription factor binding to DNA. Identification of specific transcription factor binding sites in the cis-regulatory regions of genes makes it possible to list direct targets of transcription factors, model transcriptional regulatory networks, and mine other associated datasets for relevant targets for experimental and clinical manipulation. We have developed a web-based tool to assist biologists in efficiently carrying out the analysis of genes from studies of specific transcription factors or otherwise. The batch extraction and analysis of cis-regulatory regions (BEARR) facilitates identification, extraction, and analysis of regulatory regions from the large amount of data that is typically generated in genome-wide studies. This chapter highlights features and serves as a tutorial for using this publicly available software. The URL is http://giscompute.gis.a-star.edu.sg/~vega/BEARR1.0/.

Discovery of estrogen receptor alpha target genes and response elements in breast tumor cells.

BACKGROUND: Estrogens and their receptors are important in human development, physiology and disease. In this study, we utilized an integrated genome-wide molecular and computational approach to characterize the interaction between the activated estrogen receptor (ER) and the regulatory elements of candidate target genes. RESULTS: Of around 19,000 genes surveyed in this study, we observed 137 ER-regulated genes in T-47D cells, of which only 89 were direct target genes. Meta-analysis of heterogeneous in vitro and in vivo datasets showed that the expression profiles in T-47D and MCF-7 cells are remarkably similar and overlap with genes differentially expressed between ER-positive and ER-negative tumors. Computational analysis revealed a significant enrichment of putative estrogen response elements (EREs) in the cis-regulatory regions of direct target genes. Chromatin immunoprecipitation confirmed ligand-dependent ER binding at the computationally predicted EREs in our highest ranked ER direct target genes, NRIP1, GREB1 and ABCA3. Wider examination of the cis-regulatory regions flanking the transcriptional start sites showed species conservation in mouse-human comparisons in only 6% of predicted EREs. CONCLUSIONS: Only a small core set of human genes, validated across experimental systems and closely associated with ER status in breast tumors, appear to be sufficient to induce ER effects in breast cancer cells. That cis-regulatory regions of these core ER target genes are poorly conserved suggests that different evolutionary mechanisms are operative at transcriptional control elements than at coding regions. These results predict that certain biological effects of estrogen signaling will differ between mouse and human to a larger extent than previously thought.