Transcription of angiogenin and ribonuclease 4 is regulated by RNA polymerase III elements and a CCCTC binding factor (CTCF)-dependent intragenic chromatin loop

Area of Science:

• Molecular Biology
• Gene Regulation
• Cancer Research

Background:

• Angiogenin (ANG) and Ribonuclease 4 (RNASE4) are crucial secreted ribonuclease superfamily members involved in cancer and neurodegenerative diseases.
• The shared genetic regions and promoter activities of ANG and RNASE4 genes suggest complex regulatory mechanisms that remain largely uncharacterized.

Purpose of the Study:

• To elucidate the structure and regulatory mechanisms of the promoter regions shared by ANG and RNASE4.
• To identify the specific elements and factors involved in the transcriptional regulation of these genes.

Main Methods:

• Characterization of promoter regions and definition of transcription start sites for ANG and RNASE4.
• Analysis of the influence of RNA polymerase III (Pol III) elements on gene expression.
• Investigation of CCCTC binding factor (CTCF) binding sites and their role in chromatin structure and gene regulation.

Main Results:

• Identified functional RNA polymerase III (Pol III) elements within the promoter region that modulate ANG and RNASE4 expression in a position- and orientation-dependent manner.
• Discovered an intragenic chromatin loop formed between two CTCF binding sites, which preferentially enhances ANG transcription.
• Demonstrated that Pol III elements can directly influence RNA polymerase II (Pol II) gene transcription.

Conclusions:

• The ANG and RNASE4 gene locus exhibits a multilayered transcriptional regulation involving both Pol III elements and CTCF-mediated chromatin looping.
• CTCF-dependent chromatin loops can differentially regulate transcription of genes sharing common regulatory elements.
• These findings provide direct evidence for the interplay between Pol III and Pol II transcription machinery and highlight novel regulatory strategies in gene expression.