To determine how microproteins function in the cell, researchers interrogate their interactions with other proteins. One way to do this is to genetically tag the microprotein of interest with a peptide called FLAG and then isolate it and its interacting partners using antibodies that bind to the tag. Alternatively, researchers can use a tag called APEX2 that labels nearby interacting proteins. In both cases, the isolated protein complexes are analyzed using proteomic and biochemical methods, and the results can shed light on the functions of the microproteins themselves.
Tagging a microprotein called cell cycle regulator of nonhomologous end joining (CYREN) revealed its role in regulating DNA repair. Researchers linked a DNA sequence encoding a short peptide called FLAG to the gene encoding CYREN. The FLAG-tagged microprotein sequence was then expressed in cultured human embryonic kidney cells, which were collected, lysed, and incubated with anti-FLAG antibodies bound to beads.
Putative function: ...
