| Budget Amount *help |
¥4,110,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥510,000)
Fiscal Year 2007: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2006: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
X-linked alpha thalassemia mental retardation (ATR-X) syndrome is caused by mutations in the ATRX gene. One of mutational hot spots is the region corresponding to the Zn finger domain of unknown function (ZnF1, ZnF2, and ZnF3) in its amino terminus. To reveal the cause of this genetic disorder, we explored the possibility that this domain functions as a ubiquitin ligase and that ubiquitinylation of chromatine related factors by this domain regulates gene expression.
1. (1) We have shown the Zn finger domain is ubiquitinylated both in vivo and in vitro. (2) Ubiquitin ligase activity requires not only ZnF2-ZnF3 homologous to RING/PHD fingers known as ubiquitin ligases but also ZnF1 in their N-terminus. (3) Mutations of the Zn finger domain found in the ATR-X syndrome diminish the ligase activity. These results suggest that the Zn finger domain of ATRX constitutes a new family of ubiquitin ligase and that reduction of ligase activity gives rise to the ATR-X syndrome.
2. Far UV CD measurements of wild type ZnF (1, 2, 3) and its mutant in ZnF1 have indicated disruption of the ZnF1 structure alone results in distortion of the overall structure of the Zn finger domain, which might lead to loss of its enzymatic activity.
3. Three human genes (ATRXLα, ATRXβ, and ATRXLγ) encoding proteins with ATRX-like Zn finger domains were identified and isolated ATRX-like Zn finger domains from these proteins were also shown to have ubiquitin ligase activity in vitro.
4. Drosophila ATRX genes were identified. Interestingly, Drosophila ATRX is encoded by two genes ; namely, dATRXN and dATRXC which contain the Zn finger domain and the helicase domain, respectively. The ubiquitin ligase activity was not, however, detected in the isolated Zn finger domain of dATRXN. HP1 and HDAC1, known to interact with ATRX, were not ubiquitinylated by ATRX.
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