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Control of chromosome stability by the beta-TrCP-REST-Mad2 axis.

ABSTRACT: REST/NRSF (repressor-element-1-silencing transcription factor/neuron-restrictive silencing factor) negatively regulates the transcription of genes containing RE1 sites. REST is expressed in non-neuronal cells and stem/progenitor neuronal cells, in which it inhibits the expression of neuron-specific genes. Overexpression of REST is frequently found in human medulloblastomas and neuroblastomas, in which it is thought to maintain the stem character of tumour cells. Neural stem cells forced to express REST and c-Myc fail to differentiate and give rise to tumours in the mouse cerebellum. Expression of a splice variant of REST that lacks the carboxy terminus has been associated with neuronal tumours and small-cell lung carcinomas, and a frameshift mutant (REST-FS), which is also truncated at the C terminus, has oncogenic properties. Here we show, by using an unbiased screen, that REST is an interactor of the F-box protein beta-TrCP. REST is degraded by means of the ubiquitin ligase SCF(beta-TrCP) during the G2 phase of the cell cycle to allow transcriptional derepression of Mad2, an essential component of the spindle assembly checkpoint. The expression in cultured cells of a stable REST mutant, which is unable to bind beta-TrCP, inhibited Mad2 expression and resulted in a phenotype analogous to that observed in Mad2(+/-) cells. In particular, we observed defects that were consistent with faulty activation of the spindle checkpoint, such as shortened mitosis, premature sister-chromatid separation, chromosome bridges and mis-segregation in anaphase, tetraploidy, and faster mitotic slippage in the presence of a spindle inhibitor. An indistinguishable phenotype was observed by expressing the oncogenic REST-FS mutant, which does not bind beta-TrCP. Thus, SCF(beta-TrCP)-dependent degradation of REST during G2 permits the optimal activation of the spindle checkpoint, and consequently it is required for the fidelity of mitosis. The high levels of REST or its truncated variants found in certain human tumours may contribute to cellular transformation by promoting genomic instability.

SUBMITTER: Guardavaccaro D

PROVIDER: S-EPMC2707768 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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Control of chromosome stability by the beta-TrCP-REST-Mad2 axis.

Guardavaccaro Daniele D Frescas David D Dorrello N Valerio NV Peschiaroli Angelo A Multani Asha S AS Cardozo Timothy T Lasorella Anna A Iavarone Antonio A Chang Sandy S Hernando Eva E Pagano Michele M

Nature 20080301 7185

REST/NRSF (repressor-element-1-silencing transcription factor/neuron-restrictive silencing factor) negatively regulates the transcription of genes containing RE1 sites. REST is expressed in non-neuronal cells and stem/progenitor neuronal cells, in which it inhibits the expression of neuron-specific genes. Overexpression of REST is frequently found in human medulloblastomas and neuroblastomas, in which it is thought to maintain the stem character of tumour cells. Neural stem cells forced to expre ...[more]

PMID: 18354482

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Project description:Upregulation of protein neddylation occurs in numerous types of human cancer, including liver cancer. MLN4924, a potent neddylation‑inhibiting pharmacological agent, demonstrates anticancer ability in numerous cancers. However, the sensitivity of MLN4924 in liver cancer remains unsatisfactory due to factors causing resistance. RT‑qPCR and western blotting were utilized to assess the mRNA and protein levels of genes, respectively. Cell Counting Kit‑8 assay and colony formation assays were employed to assess cell viability and proliferation. The pathway of protein degradation and stability were determined by western blotting after treatment with MG132 and cycloheximide. An immunoprecipitation assay was utilized to detect the ubiquitination of protein. An in vitro ubiquitination assay was used to determine the ubiquitin linkage. To the best of our knowledge, the present study was the first to demonstrate that NF‑κB inhibitor α (IκBα) downregulation and subsequent inflammation in response to MLN4924 limited the antitumor potential of MLN4924. Ectopic expression of IκBα enhanced the antitumor potential of MLN4924 in liver cancer cells. Moreover, the results of the present study demonstrated that MLN4924 decreased IκBα via promoting the K48 linkage of ubiquitin to IκBα. Mechanistic studies demonstrated that MLN4924 enhanced the protein stability of β‑transducin repeat‑containing protein (β‑TrCP), promoting the ubiquitination of IκBα, which led to the ubiquitin‑mediated degradation of IκBα. In addition, the results of the present study also demonstrated that β‑TrCP knockdown markedly inhibited MLN4924 from suppressing the growth of liver cancer cells, via attenuating MLN4924‑mediated IκBα downregulation and inflammation. Collectively, these results indicated that the β‑TrCP/IκBα/inflammation pathway may act as a novel resistance factor of MLN4924, and targeting β‑TrCP may be beneficial for the treatment of liver cancer.

Dataset Information

Control of chromosome stability by the beta-TrCP-REST-Mad2 axis.

Publications

Control of chromosome stability by the beta-TrCP-REST-Mad2 axis.

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