Phosphorylation of a Human Microprotein Promotes Dissociation of Biomolecular Condensates

Proteogenomic identification of translated
small open reading frames
in humans has revealed thousands of microproteins, or polypeptides
of fewer than 100 amino acids, that were previously invisible to geneticists.
Hundreds of microproteins have been shown to be essential for cell
growth and proliferation, and many regulate macromolecular complexes.
However, the vast majority of microproteins remain functionally uncharacterized,
and many lack secondary structure and exhibit limited evolutionary
conservation. One such intrinsically disordered microprotein is NBDY,
a 68-amino acid component of membraneless organelles known as P-bodies.
In this work, we show that NBDY can undergo liquid–liquid phase
separation, a biophysical process thought to underlie the formation
of membraneless organelles, in the presence of RNA in vitro. Phosphorylation of NBDY drives liquid phase remixing in
vitro and macroscopic P-body dissociation in cells undergoing
growth factor signaling and cell division. These results suggest that
NBDY phosphorylation enables regulation of P-body dynamics during
cell proliferation and, more broadly, that intrinsically disordered
microproteins may contribute to liquid–liquid phase separation
and remixing behavior to affect cellular processes.