Most human proteins made in both nucleus and cytoplasm turn over within minutes

PLoS One. 2014 Jun 9;9(6):e99346. doi: 10.1371/journal.pone.0099346. eCollection 2014.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / metabolism
  • Animals
  • Cell Line
  • Cell Nucleus / metabolism*
  • Cytoplasm / metabolism*
  • Humans
  • Nonsense Mediated mRNA Decay
  • Peptides / metabolism
  • Protein Biosynthesis
  • Protein Transport
  • Proteins / metabolism*
  • Puromycin / pharmacology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Ribosomes / metabolism
  • Time Factors

Substances

  • Amino Acids
  • Peptides
  • Proteins
  • RNA, Messenger
  • Puromycin