Cul4A targets p27 for degradation and regulates proliferation, cell cycle exit, and differentiation during erythropoiesis

Binghui Li, Nan Jia, Reuben Kapur, Kristin T. Chun

Research output: Contribution to journalArticlepeer-review

67 Scopus citations


As erythroid progenitors differentiate into precursors and finally mature red blood cells, lineage-specific genes are induced, and proliferation declines until cell cycle exit. Cul4A encodes a core subunit of a ubiquitin ligase that targets proteins for ubiquitin-mediated degradation, and Cul4A-haploinsufficient mice display hematopoietic dysregulation with fewer multipotential and erythroid-committed progenitors. In this study, stress induced by 5-fluorouracil or phenylhydrazine revealed a delay in the recovery of erythroid progenitors, early precursors, and normal hematocrits in Cul4A+/- mice. Conversely, overexpression of Cul4A in a growth factor-dependent, proerythroblast cell line increased proliferation and the proportion of cells in S phase. When these proerythroblasts were induced to terminally differentiate, endogenous Cul4A protein expression declined 3.6-fold. Its enforced expression interfered with erythrocyte maturation and cell cycle exit and, instead, promoted proliferation. Furthermore, p27 normally accumulates during erythroid terminal differentiation, but Cul4A-enforced expression destabilized p27 and attenuated its accumulation. Cul4A and p27 proteins coimmunoprecipitate, indicating that a Cul4A ubiquitin ligase targets p27 for degradation. These findings indicate that a Cul4A ubiquitin ligase positively regulates proliferation by targeting p27 for degradation and that Cul4A down-regulation during terminal erythroid differentiation allows p27 to accumulate and signal cell cycle exit.

Original languageEnglish (US)
Pages (from-to)4291-4299
Number of pages9
Issue number11
StatePublished - Jun 1 2006

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology

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