Gene loops enhance transcriptional directionality.

Area of Science:

• Molecular Biology
• Genetics
• Gene Regulation

Background:

• Eukaryotic genomes undergo extensive transcription, producing both messenger RNAs (mRNAs) and noncoding RNAs (ncRNAs).
• Noncoding RNAs often originate from bidirectional promoters, leading to transcription in opposite directions.
• Understanding the regulation of divergent transcription is crucial for comprehending genome expression.

Purpose of the Study:

• To investigate the role of gene-loop conformation in regulating divergent transcription.
• To determine the impact of the Ssu72 protein on the synthesis of promoter-associated ncRNAs.
• To elucidate how actively transcribed genes influence the directionality of transcription.

Main Methods:

• Analysis of gene-loop formation in actively transcribed mRNA genes.
• Investigating the function of the Ssu72 protein in transcriptional regulation.
• Assessing the synthesis of Ssu72-restricted transcripts (SRTs) upon Ssu72 inactivation or gene mutation.

Main Results:

• Actively transcribed mRNA genes adopt a gene-loop conformation that restricts divergent ncRNA transcription.
• Inactivation of the Ssu72 protein, a key factor in gene-loop formation, significantly increases SRT synthesis.
• Disruption of individual gene loops through mutation also leads to enhanced SRT production.
• Gene-loop conformation enforces transcriptional directionality at bidirectional promoters.

Conclusions:

• Gene-loop formation is a critical mechanism for controlling divergent transcription and maintaining transcriptional directionality.
• The Ssu72 protein plays a vital role in establishing and maintaining gene loops, thereby suppressing ncRNA synthesis.
• These findings reveal a novel layer of gene regulation ensuring the precise expression of coding and noncoding RNAs.