Nuclear interaction partner of ALK (NIPA) is an F-box-containing protein that defines a nuclear skp1 cullin F-box (SCF)-type ubiquitin E3 ligase (SCFNIPA) implicated in the regulation of mitotic entry. The SCFNIPA complex targets nuclear cyclin B1 for ubiquitination in interphase, whereas phosphorylation of NIPA in late G2 phase and mitosis inactivates the complex to allow for accumulation of cyclin B1. Here, we identify the region of NIPA that mediates binding to its substrate cyclin B1. In addition to the recently described serine residue 354, we specify 2 new residues, Ser-359 and Ser-395, implicated in the phosphorylation process at G2/M within this region. Moreover, we found cyclin B1/Cdk1 to phosphorylate NIPA at Ser-395 in mitosis. Mutation of both Ser-359 and Ser-395 impaired effective inactivation of the SCFNIPA complex, resulting in reduced levels of mitotic cyclin B1. These data are compatible with a process of sequential NIPA phosphorylation where cyclin B1/Cdk1 amplifies phosphorylation of NIPA once an initial phosphorylation event has dissociated the SCFNIPA complex. Thus, cyclin B1/Cdk1 may contribute to the regulation of its own abundance in early mitosis.
characterized NIPA as an F-box like protein that defines a ubiquitin E3 ligase
(SCFNIPA) which targets nuclear cyclin B1 for degradation and thereby
contributes to the timing of mitotic entry. Intriguingly, phosphorylation
of NIPA in late G2 phase leads to dissociation of NIPA from the SCF core complex,
thus restricting activity of the SCFNIPA complex to interphase , . Here,
we report that phosphorylated NIPA is degraded at mitotic exit in an APC/CCdh1-dependent
[Show abstract][Hide abstract] ABSTRACT: NIPA (Nuclear Interaction Partner of Alk kinase) is an F-box like protein
that targets nuclear Cyclin B1 for degradation. Integrity and therefore activity
of the SCFNIPA E3 ligase is regulated by cell-cycle-dependent phosphorylation
of NIPA, restricting substrate ubiquitination to interphase. Here we show
that phosphorylated NIPA is degraded in late mitosis in an APC/CCdh1-dependent
manner. Binding of the unphosphorylated form of NIPA to Skp1 interferes with
binding to the APC/C-adaptor protein Cdh1 and therefore protects unphosphorylated
NIPA from degradation in interphase. Our data thus define a novel mode of
regulating APC/C-mediated ubiquitination.
PLoS ONE 12/2011; 6(12):e28998. DOI:10.1371/journal.pone.0028998 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The F-Box protein NIPA (Nuclear Interaction Partner of Alk) binds specifically to Skp1 and defines an active ubiquitin E3 ligase (SCF<sup>NIPA</sup>) which targets nuclear cyclin B1 for degradation. Phosphorylation of NIPA in late G2 leads to dissociation of NIPA from the SCF core complex, thus restricting activity of the SCF<sup>NIPA</sup> to interphase. In this work it is shown that the phosphorylated form of NIPA is itself degraded in late mitosis by the ubiquitin-proteasome system. This degradation of NIPA is mediated by the APC<sup>Cdh1</sup> E3 ligase and is regulated by the association of NIPA to the SCF core subunit Skp1.
In the second part of this work it is shown that NIPA is phosphorylated after DNA-damage, leading to a cell cycle-independent inactivation of the SCF<sup>NIPA</sup> complex. This phosphorylation is dependent on the phosphatidylinositolkinase-like kinase ATR. It is further shown that NIPA modulates the DNA-damage response after UVC-treatment.
[Show abstract][Hide abstract] ABSTRACT: Tyrosine kinases are involved in the pathogenesis of most cancers. However, few tyrosine kinases have been shown to have a well-defined pathogenetic role in lymphomas. The anaplastic lymphoma kinase (ALK) is the oncogene of most anaplastic large cell lymphomas (ALCL), driving transformation through many molecular mechanisms. In this Review, we will analyse how translocations or deregulated expression of ALK contribute to oncogenesis and how recent genetic or pharmacological tools, aimed at neutralizing its activity, can represent the basis for the design of powerful combination therapies.
Nature Reviews Cancer 02/2008; 8(1):11-23. DOI:10.1038/nrc2291 · 37.40 Impact Factor
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