Structure-function analysis of Qk1: a lethal point mutation in mouse quaking prevents homodimerization

Area of Science:

• Molecular Biology
• Genetics
• Developmental Biology

Background:

• Qk1 is an RNA-binding protein belonging to the KH domain family.
• The GSG domain of Qk1 is crucial for its function.
• A specific mutation (Glu48Gly) in the GSG domain causes embryonic lethality in mice.

Purpose of the Study:

• To investigate the function of the Qk1 GSG domain.
• To elucidate the mechanism behind the embryonic lethality associated with the Qk1 mutation.

Main Methods:

• In situ chemical cross-linking to study protein interactions.
• Site-directed mutagenesis to create the Qk1:EG mutant.
• Cell viability assays (apoptosis induction) in NIH 3T3 cells.

Main Results:

• The Qk1 GSG domain mediates both RNA binding and self-association.
• Qk1 proteins form homodimers in vivo.
• The Glu48Gly mutation abolishes Qk1 self-association but not RNA binding.
• Expression of Qk1 or Qk1:EG induces apoptosis; Qk1:EG is more potent.

Conclusions:

• Qk1 self-association via the GSG domain is essential for its function.
• The embryonic lethality in quaking mice is likely due to the lack of Qk1 self-association.