Nopp 140 shuttles on tracks between nucleolus and cytoplasm

U. Thomas Meier, Günter Blobel

Research output: Contribution to journalArticle

322 Scopus citations

Abstract

Nopp140 is a nucleolar phosphoprotein of 140 kd that we originally identified and purified as a nuclear localization signal (NLS)-binding protein. Molecular characterization revealed a 10-fold repeated motif of highly conserved acidic serine clusters that contain an abundance of phosphorylation consensus sites for casein kinase II (CK II). Indeed, Nopp140 is one of the most phosphoryaated proteins in the cell, and NLS binding was dependent on phosphorylation. Nopp140 was shown to shuttle between the nucleolus and the cytoplasm. Shuttling is likely to proceed on tracks that were revealed by immunoelectron microscopy. These tracks extend from the dense fibrillar component of the nucleolus across the nucleoplasm to some nuclear pore complexes. We suggest that Nopp140 functions as a chaperone for import into and/or export from the nucleolus.

Original languageEnglish (US)
Pages (from-to)127-138
Number of pages12
JournalCell
Volume70
Issue number1
DOIs
StatePublished - Jul 10 1992

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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