Size matters: conserved proteins function in length-dependent nuclear export of circular RNAs

Area of Science:

• Molecular Biology
• Cell Biology
• RNA Biology

Background:

• Circular RNAs (circRNAs) are abundant RNA molecules with crucial biological roles.
• The subcellular localization and trafficking of circRNAs, particularly nuclear export, remain largely uncharacterized.

Purpose of the Study:

• To investigate the mechanisms governing the nuclear export of circular RNAs.
• To identify the proteins and regulatory elements involved in circRNA trafficking.

Main Methods:

• Utilized *Drosophila* and human cell models.
• Investigated the role of *Drosophila* Hel25E and its human homologs (UAP56, URH49) in circRNA nuclear export.
• Analyzed the length-dependent nature of circRNA export and the underlying molecular determinants.

Main Results:

• Identified *Drosophila* Hel25E and human UAP56/URH49 as essential factors for circRNA nuclear export.
• Demonstrated that circRNA nuclear export is surprisingly dependent on RNA length.
• Uncovered a four-amino-acid motif in Hel25E and homologs responsible for sensing RNA length.

Conclusions:

• This study provides the first mechanistic insights into the nuclear export of circular RNAs.
• The findings reveal a novel length-dependent regulation of circRNA trafficking mediated by specific protein motifs.
• This work advances our understanding of circRNA biology and subcellular transport.