| Budget Amount *help |
¥17,750,000 (Direct Cost: ¥15,500,000、Indirect Cost: ¥2,250,000)
Fiscal Year 2007: ¥9,750,000 (Direct Cost: ¥7,500,000、Indirect Cost: ¥2,250,000)
Fiscal Year 2006: ¥8,000,000 (Direct Cost: ¥8,000,000)
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| Research Abstract |
CHFR which contains a RING domain and has ubiquitin ligase activity, a novel mitotic checkpoint gene delays chromosome condensation in cells treated with microtubule poisons. CHFR is inactivated by promoter methylation, and cancer cells lacking CHFR are sensitive to microtubule inhibitors.
(1) Proteins interacting with CHFR, mitotic-checkpoint ubiquitin ligase.
In this study, we isolated cellular proteins capable of interacting with CHFR using yeast two-hybrid method to clarify the function of CHFR. As a result of the screening, we isolated canonical and noncanonical E2 ubiquitin conjugating enzymes as CHFR interacting proteins, which are involved in proteolytic and non-proteolytic ubiquitination respectively. This raises the possibility that CHFR is switching canonical and noncanonical ubiquitination depending on the situation of cells.On the other hand, we isolated gadd34 which interacted with the FHA domain of CHFR. Furthermore, CHFR moved in part from nucleus to cytoplasm in the pres
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ence of microtubule inhibitor docetaxel, which enabled colocalization of CHFR and gadd34 in cytoplasm. This colocalization was followed by cell death. These suggest that gadd34 and CHFR cooperate to mediate cell death in response to mitotic stress.
(2) CHFR mitotic checkpoint protein inhibits the transcriptional activity of NF-kB.
To clarify the molecular mechanisms by which CHFR modulates tumor growth, our analysis focused on transcriptional regulation mediated by CHFR. Using microarray analysis, we found that CHFR downregulated NF-kB signaling. NF-kB-dependent luciferase assay demonstrated that overexpression of CHFR inhibited NF-kB signaling. Moreover, knockdown of CHFR activated the NF-kB activity. Furthermore, we found that IL-8, one of the NF-kB target genes, was regulated by CHFR. mRNA and protein levels of IL-8 were significantly repressed by overexpression of CHFR. Altogether, our findings reveal a novel function of CHFR as a regulator of NF-kB signaling, and which might account for tumor suppression by CHFR. Less
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