Emerging Hallmarks of Functional Proteins Encoded by Non-Canonical ORFs.

Defining the protein-coding genome is essential for biomedical research. Over the past decade, dozens of novel proteins encoded by non-canonical open-reading frames (ncORFs), which are ORFs not annotated as protein-coding in reference databases, have been discovered. Although translation products have been detected for thousands of ncORFs, the cellular functions of their encoded proteins (microproteins) remain largely unknown. To advance understanding of ncORF-encoded dark proteomes, we compiled a manually curated catalogue of 71 putatively functional microproteins reported in recent years, including sequences, precise genomic coordinates, and detailed metadata. Comparative analyses with canonical proteins revealed both shared and distinct physicochemical and structural features of microproteins. We further summarized their cellular roles and identified emerging hallmarks related to their expression, evolution, and function. Together, this resource and analyses provide a foundation for systematic discovery and characterization of functional microproteins in the future.