title: Most human proteins made in both nucleus and cytoplasm turn over within minutes.
abstract: In bacteria, protein synthesis can be coupled to transcription, but in eukaryotes it is believed to occur solely in the cytoplasm. Using pulses as short as 5 s, we find that three analogues--L-azidohomoalanine, puromycin (detected after attaching fluors using 'click' chemistry or immuno-labeling), and amino acids tagged with 'heavy' 15N and 13C (detected using secondary ion mass spectrometry)--are incorporated into the nucleus and cytoplasm in a process sensitive to translational inhibitors. The nuclear incorporation represents a significant fraction of the total, and labels in both compartments have half-lives of less than a minute; results are consistent with most newly-made peptides being destroyed soon after they are made. As nascent RNA bearing a premature termination codon (detected by fluorescence in situ hybridization) is also eliminated by a mechanism sensitive to a translational inhibitor, the nuclear turnover of peptides is probably a by-product of proof-reading the RNA for stop codons (a process known as nonsense-mediated decay). We speculate that the apparently-wasteful turnover of this previously-hidden ('dark-matter') world of peptide is involved in regulating protein production.
authors.affiliation: Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
authors.forename: Sabyasachi
authors.initials: S
authors.lastname: Baboo
authors.affiliation: Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom.
authors.forename: Bhaskar
authors.initials: B
authors.lastname: Bhushan
authors.affiliation: Department of Materials, University of Oxford, Oxford, United Kingdom.
authors.forename: Haibo
authors.initials: H
authors.lastname: Jiang
authors.affiliation: Department of Materials, University of Oxford, Oxford, United Kingdom.
authors.forename: Chris R M
authors.initials: CR
authors.lastname: Grovenor
authors.affiliation: Centre d'Immunologie de Marseille-Luminy, Aix-Marseille Université, Marseille, France; Institut National de la Santé et de la Recherche Médicale, U1104, Marseille, France; Centre National de la Recherche Scientifique, Unités Mixtes de Recherche 7280, Marseille, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Pierre
authors.affiliation: Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom.
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Davis
authors.affiliation: Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Cook
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D006801:Humans; D059365:Nonsense Mediated mRNA Decay; D010455:Peptides / Q000378:metabolism; D014176:Protein Biosynthesis; D021381:Protein Transport; D011506:Proteins / Q000378:metabolism*; D011691:Puromycin / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism; D013997:Time Factors
chemical_list: D000596:Amino Acids; D010455:Peptides; D011506:Proteins; D012333:RNA, Messenger; D011691:Puromycin