Construction and validation of a novel dual reporter vector for studying mammalian bidirectional promoters

• We describe a novel vector to study mammalian bidirectional promoters.
• Bidirectional promoters are a common feature in mammalian genomes, but few large-scale studies have been done.
• We validated our new tool with a known human bidirectional promoter (between OSGEP and APEX genes).
• To our knowledge, we show for the first time the use of flow cytometry to study the activity of a bidirectional promoter.

Regulation of gene expression plays important role in cellular functions. With the development of sequencing techniques, more and more genomes are available and genome-wide analyses of genomic structures that may affect gene expression regulation are now possible. Analyses of several genomes have found a class of regulatory regions that contain elements that initiate transcription of two different genes positioned with a head-to-head arrangement in two opposite directions. These regulatory regions are known as bidirectional promoters. Although bidirectional promoters have been known for years, recent genome-scale studies have shown that the regulation of the expression of up to 10% of the genes are controlled by bidirectional promoters. These findings are based mostly on computational work and only a limited number of putative bidirectional promoters have been experimentally validated. Developing methods to study bidirectional promoters will allow researchers to understand how these regions are regulated and the roles that divergent transcription plays in the expression of genes. Here, we have developed a novel dual-fluorescence reporter gene vector to study the transcriptional output of mammalian bidirectional promoters. We demonstrate that this vector is capable of expressing reporter genes under the control of bidirectional promoters, using the known human OSGEP/APEX bidirectional promoter.