Quaking isoforms cooperate to promote the mesenchymal phenotype

Area of Science:

• Molecular Biology
• Cell Biology
• RNA Biology

Background:

• The RNA-binding protein Quaking (QKI) regulates mRNA processing, including alternative splicing.
• QKI is induced during epithelial-mesenchymal transition (EMT) and promotes a mesenchymal splicing signature.
• QKI has three major isoforms (QKI-5, QKI-6, QKI-7) with distinct cellular localizations and functions.

Purpose of the Study:

• To investigate the distinct and cooperative roles of QKI isoforms in promoting the mesenchymal phenotype during EMT.
• To characterize the functions of the cytoplasmic QKI-6 and QKI-7 isoforms in the context of EMT.

Main Methods:

• CRISPR-mediated depletion of QKI in a human mammary epithelial cell model of EMT.
• Expression of individual and combined QKI isoforms.
• Analysis of mesenchymal morphology, cell migration, and alternative splicing.

Main Results:

• QKI-5 is necessary for inducing mesenchymal morphology.
• Co-expression of QKI-5 with QKI-6 or QKI-7 enhanced mesenchymal morphology and cell migration.
• QKI-6 and QKI-7 can localize to the nucleus and contribute to alternative splicing of target genes.

Conclusions:

• QKI isoforms function dynamically and cooperatively to promote the mesenchymal phenotype.
• Both nuclear and cytoplasmic QKI isoforms play critical roles in EMT.
• Understanding QKI isoform function provides insights into cancer progression and metastasis.