Transcription factor binding and modified histones in human bidirectional promoters

Area of Science:

• Genomics
• Molecular Biology
• Gene Regulation

Background:

• Bidirectional promoters regulate two downstream genes (divergent genes) and constitute approximately 11% of the human genome.
• Understanding their regulatory mechanisms is crucial for comprehending gene expression.
• Previous studies have identified some motifs and factors associated with these promoters.

Purpose of the Study:

• To comprehensively analyze the DNA sequence motifs, transcription factor binding, and histone modifications associated with bidirectional promoters.
• To compare these features with those of unidirectional promoters.
• To investigate the role of the GABPA transcription factor in bidirectional promoter regulation.

Main Methods:

• Analysis of DNA sequence motifs and transcription factor binding data.
• Chromatin immunoprecipitation (ChIP) followed by quantitative PCR for GABPA binding.
• Analysis of histone modification data (H3K4me2, H3K4me3, H3ac) and RNA polymerase II occupancy.
• Whole-genome microarray data analysis.

Main Results:

• A small set of motifs (e.g., GABPA, MYC, E2F1) are overrepresented in bidirectional promoters, while most vertebrate motifs are underrepresented.
• GABPA binds more frequently to bidirectional promoters than unidirectional promoters.
• Active transcription signatures are enriched around bidirectional promoters, with 68% of divergent genes transcribed compared to 44% of all human genes.

Conclusions:

• Bidirectional promoters possess distinct motif compositions and regulatory characteristics compared to unidirectional promoters.
• The transcription factor GABPA plays a significant role in regulating bidirectional promoters.
• A higher proportion of genes regulated by bidirectional promoters are actively transcribed.