Dual Function of DNA Sequences: Protein-Coding Sequences Function as Transcriptional Enhancers

Area of Science:

• Genomics
• Molecular Biology
• Epigenetics

Background:

• The human genome contains vast noncoding regions with regulatory elements like enhancers.
• Protein-coding sequences (exons) comprise only ~1.5% of the genome.
• Exons can also function as enhancers (eExons), possessing dual roles.

Purpose of the Study:

• To investigate the prevalence and functional consequences of enhancer-exons (eExons).
• To analyze the impact of mutations within eExons on both protein-coding and regulatory functions.
• To understand the cell-type-specific effects of eExon mutations.

Main Methods:

• Utilized advanced sequencing technologies to identify potential regulatory functions in mammalian protein-coding sequences.
• Performed single-nucleotide resolution analysis of enhancer activity for eExons in liver cells.
• Examined transcription factor-binding sites and mutation effects.

Main Results:

• Protein-coding sequences with regulatory functions (eExons) are overrepresented in the genome (>6%).
• Most high-impact nucleotide changes in eExons are deleterious.
• Deleterious mutations correlate with transcription factor-binding sites.
• Synonymous and non-synonymous mutations similarly affect enhancer activity.
• Enhancer activity is controlled by cell-type-specific transcription factors.

Conclusions:

• Mutations in eExons can disrupt both protein structure and enhancer activity.
• The phenotypic consequences of eExon mutations can be cell-type-specific.
• A single mutation can lead to disease through disruption of hidden regulatory functions, independent of protein-coding changes.