The quaking I-5 protein (QKI-5) has a novel nuclear localization signal and shuttles between the nucleus and the cytoplasm

Jiang Wu, Li Zhou, Kathryn Tonissen, Ronald Tee, Karen Artzt

Research output: Contribution to journalArticlepeer-review

117 Scopus citations


The mouse quaking (qk) gene is essential in both myelination and early embryogenesis. Its product, QKI, is an RNA-binding protein belonging to a growing protein family called STAR (signal transduction and activator of RNA). All members have an ~200-amino acid STAR domain, which contains a single extended heteronuclear ribonucleoprotein K homologue domain flanked by two domains called QUA1 and QUA2. We found that QKI isoforms could associate with each other, while one of the lethal mutations qkI(kt4) with a single amino acid change in QUA1 domain, leads to a loss of QKI self-interaction. This suggests that the QUA1 domain is responsible for QKI dimerization. Three QKI isoforms have different carboxyl termini and different subcellular localization. Here, using GFP fusion protein, we identified a 7-amino acid novel nuclear localization sequence in the carboxyl terminus of QKI-5, which is conserved in a subclass of STAR proteins containing SAM68 and ETLE/T-STAR. Thus, we name this motif STAR-NLS. In addition, the effects of active transcription, RNA-binding and self-interaction on QKI-5 localization were analyzed. Furthermore, using an interspecies heterokaryon assay, we found that QKI-5, but not another STAR protein ETLE, shuttles between the nucleus and the cytoplasm, which suggests that QKI-5 functions in both cell compartments.

Original languageEnglish (US)
Pages (from-to)29202-29210
Number of pages9
JournalJournal of Biological Chemistry
Issue number41
StatePublished - Oct 8 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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