Brap2 functions as a cytoplasmic retention protein for p21 during monocyte differentiation

Minoru Asada, Kazuhiro Ohmi, Domenico Delia, Shin Enosawa, Seiichi Suzuki, Akira Yuo, Hidenori Suzuki, Shuki Mizutani

Research output: Contribution to journalArticlepeer-review


The cell cycle inhibitor p21 plays an important role in monocytic cell differentiation, during which it translocates from the nucleus to cytoplasm. This process involves the negative regulation of the p21 nuclear localization signal (NLS). Here, we sought to determine the relationship between the cytoplasmic translocation of p21 and another molecule, Brap2, a cytoplasmic protein which binds the NLS of BRCA1 and was recently reported to inactivate KSR in the Ras-activating signal pathway under the name of IMP. We report that p21 and Brap2 directly interact, both in vitro and in vivo, in a manner requiring the NLS of p21 and the C-terminal portion of Brap2. When it is cotransfected with Brap2, p21 is expressed in the cytoplasm. Monocytic differentiation of the promyelomonocytic cell lines U937 and HL60 is associated with the upregulation of Brap2 expression concomitantly with the upregulation and cytoplasmic relocalization of p21. Our results underscore the role played by Brap2 in the process of cytoplasmic translocation of p21 during monocyte differentiation.

Original languageEnglish
Pages (from-to)8236-8243
Number of pages8
JournalMolecular and Cellular Biology
Issue number18
Publication statusPublished - Sep 2004

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology


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