International consortium discovers 1,785 microproteins from non-canonical open reading frames, proposes 'peptidein' concept (mdc-berlin.de)

• Over 1,700 microproteins detected from ncORFs; increases known proteome by ~10%
• 65% of microproteins are under 50 amino acids; less than 1% of known proteins are that small
• New category 'peptidein' defined for molecules with protein-like structure but ambiguous function
• Six peptideins found pan-essential in cancer cells via CRISPR; OLMALINC peptidein involved in cell division
• Potential applications in cancer immunotherapy as many peptideins are presented on cell surfaces

"An international consortium including the Max Delbrück Center has identified 1,785 microproteins from previously overlooked non-canonical open reading frames (ncORFs) in human DNA. The study, published in Nature on May 7, 2026, analyzed 3.7 billion spectra from 95,520 mass spectrometry experiments. Most microproteins are fewer than 50 amino acids, contrasting with traditional proteins. The researchers propose a new biological concept, 'peptidein,' for these molecules whose functions are ambiguous. Six peptideins were identified as essential for cancer cell survival via CRISPR screens, including one from OLMALINC involved in cell division and DNA damage response. The findings expand the known human proteome by nearly 10% and may reveal new drug targets for cancer immunotherapy."