A Skp2 autoinduction loop and restriction point control

نویسندگان

  • Yuval Yung
  • Janice L. Walker
  • James M. Roberts
  • Richard K. Assoian
چکیده

We describe a self-amplifying feedback loop that autoinduces Skp2 during G1 phase progression. This loop, which contains Skp2 itself, p27(kip1) (p27), cyclin E-cyclin dependent kinase 2, and the retinoblastoma protein, is closed through a newly identified, conserved E2F site in the Skp2 promoter. Interference with the loop, by knockin of a Skp2-resistant p27 mutant (p27(T187A)), delays passage through the restriction point but does not interfere with S phase entry under continuous serum stimulation. Skp2 knock down inhibits S phase entry in nontransformed mouse embryonic fibroblasts but not in human papilloma virus-E7 expressing fibroblasts. We propose that the essential role for Skp2-dependent degradation of p27 is in the formation of an autoinduction loop that selectively controls the transition to mitogen-independence, and that Skp2-dependent proteolysis may be dispensable when pocket proteins are constitutively inactivated.

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عنوان ژورنال:
  • The Journal of Cell Biology

دوره 178  شماره 

صفحات  -

تاریخ انتشار 2007