No Time to Fold: Intrinsically Disordered Microproteins in Action.

Advances in genomics, proteomics, and bioinformatics have uncovered the existence of thousands of translated small open reading frames less than 100-150 codons in length that encode microproteins. In addition to their diminutive size, microproteins are also often predicted to be intrinsically disordered based on their enrichment in disordered-promoting amino acids. Microproteins have since been found to regulate diverse cellular processes, including DNA repair, mRNA decay, mitochondrial metabolism, and ribosome biogenesis, among others. While only a small fraction of microproteins have been functionally characterized, many examples have been found to act as regulators of larger proteins and protein complexes in ways similar to annotated intrinsically disordered proteins (IDPs). In this review, we summarize the functions and mechanisms of several disordered microproteins while exploring the approaches used to study their disordered nature, their regulation by post-translational modifications, and potential strategies to therapeutically target them in disease. These examples underscore how investigations of disordered microproteins deepen our understanding of how biological processes are regulated and emphasize how close collaboration between the microprotein and IDP fields can enhance these efforts.