Human DDX21 binds and unwinds RNA guanine quadruplexes

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Guanine quadruplexes (G4s) are crucial nucleic acid structures involved in cellular processes.
• RNA G4s necessitate specific unwinding enzymes, with only two previously known.
• Identifying novel G4-interacting proteins is vital for understanding G4 functions.

Purpose of the Study:

• To screen for Guanine quadruplex (G4) binding proteins in cell lysate.
• To validate the RNA helicase DDX21 as a G4 binding protein.
• To investigate the mechanism and functional implications of DDX21-G4 interactions.

Main Methods:

• Mass spectrometry-guided screening of HEK293T cell lysate.
• Biochemical assays to confirm direct protein-quadruplex RNA interactions.
• Nuclease sensitivity assays to assess G4 unwinding activity.
• Functional assays to demonstrate DDX21's effect on gene expression.

Main Results:

• DDX21 was identified as a novel Guanine quadruplex (G4) binding protein.
• Direct interaction between DDX21 and G4 RNA was confirmed, localized to the C-terminus.
• DDX21 demonstrated the ability to unwind RNA G4 structures.
• DDX21 was shown to suppress protein expression by targeting mRNA with G4s in the 3' UTR.

Conclusions:

• DDX21 is a functional RNA helicase that directly binds and unwinds Guanine quadruplexes (G4s).
• DDX21 plays a role in regulating gene expression through G4 structures in mRNA.
• This study expands the known repertoire of G4-interacting proteins and their functions.