The Human RNA Helicase DDX21 Presents a Dimerization Interface Necessary for Helicase Activity

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• DEAD-box helicases are vital for RNA metabolism and implicated in diseases.
• The role of protein oligomerization in DEAD-box helicase function remains unclear.

Purpose of the Study:

• To investigate the oligomerization state of human DEAD-box helicase DDX21.
• To determine how DDX21 oligomerization affects its biochemical activities, specifically RNA helicase and G-quadruplex remodeling.

Main Methods:

• Solution small-angle X-ray scattering (SAXS) to analyze protein structure and flexibility.
• In vitro helicase assays to assess ATP-dependent unwinding and ATP-independent remodeling activities.

Main Results:

• DDX21 exists as a dimer in solution, featuring a central dimerization domain.
• Arg/Gly-rich C termini are important for high-affinity RNA binding.
• An intact DDX21 dimer is essential for both double-stranded RNA unwinding and G-quadruplex remodeling.

Conclusions:

• Oligomerization is a key regulatory mechanism for DEAD-box helicase activity.
• DDX21 dimerization is critical for its distinct helicase and remodeling functions.
• Understanding DDX21 oligomerization provides insights into RNA metabolism regulation.