Human FASTK preferentially binds single-stranded and G-rich RNA

Area of Science:

• Molecular Biology
• RNA Biology
• Biochemistry

Background:

• Fas-activated serine/threonine kinase (FASTK) is crucial for mRNA fate regulation.
• FASTK variants influence mRNA splicing, translation, and degradation.
• Specific RNA recognition mechanisms of FASTK were previously unknown.

Purpose of the Study:

• To investigate the direct RNA binding properties of human FASTK.
• To elucidate the structural basis of FASTK-RNA interactions.
• To understand FASTK's role in mitochondrial mRNA stability.

Main Methods:

• Purification of human FASTK.
• In vitro RNA binding assays using G-rich oligonucleotides.
• Small-Angle X-ray Scattering (SAXS) for structural analysis.
• Point mutagenesis to identify RNA-binding regions.

Main Results:

• FASTK directly binds single-stranded, G-rich RNA, including G-quadruplex forming sequences.
• FASTK protects mitochondrial mRNAs from degradation by the degradosome.
• SAXS revealed FASTK as a monomer with an extended conformation in solution.
• Mutagenesis identified an exposed RNA-binding interface in the central helical region.

Conclusions:

• FASTK possesses intrinsic RNA-binding capabilities favoring specific G-rich structures.
• FASTK's RNA binding directly contributes to mitochondrial mRNA stability.
• The structural and biochemical properties of FASTK underpin its diverse roles in mRNA metabolism.