Research article

Complex organizational structure of the genome revealed by genome-wide analysis of single and alternative promoters in Drosophila melanogaster

Qianqian Zhu^1,2 and Marc S Halfon^1,3,4,5

¹Department of Biochemistry, Buffalo, NY 14214, USA

²Department of Biostatistics, Buffalo, NY 14214, USA

³Department of Biological Sciences, State University of New York at Buffalo, Buffalo, NY 14214, USA

⁴New York State Center of Excellence in Bioinformatics and the Life Sciences, Buffalo, NY 14203, USA

⁵Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA

author email corresponding author email

BMC Genomics 2009, 10:9doi:10.1186/1471-2164-10-9

Published:	7 January 2009

Abstract

Background

The promoter is a critical necessary transcriptional cis-regulatory element. In addition to its role as an assembly site for the basal transcriptional apparatus, the promoter plays a key part in mediating temporal and spatial aspects of gene expression through differential binding of transcription factors and selective interaction with distal enhancers. Although many genes have multiple promoters, little attention has been focused on how these relate to one another; nor has much study been directed at relationships between promoters of adjacent genes.

Results

We have undertaken a systematic investigation of Drosophila promoters. We divided promoters into three groups: unique promoters, first alternative promoters (the most 5' of a gene's multiple promoters), and downstream alternative promoters (the remaining alternative promoters 3' to the first). We observed distinct nucleotide distribution and sequence motif preferences among these three classes. We also investigated the promoters of neighboring genes and found that a greater than expected number of adjacent genes have similar sequence motif profiles, which may allow the genes to be regulated in a coordinated fashion. Consistent with this, there is a positive correlation between similar promoter motifs and related gene expression profiles for these genes.

Conclusions

Our results suggest that different regulatory mechanisms may apply to each of the three promoter classes, and provide a mechanism for "gene expression neighborhoods," local clusters of co-expressed genes. As a whole, our data reveal an unexpected complexity of genomic organization at the promoter level with respect to both alternative and neighboring promoters.