| Budget Amount *help |
¥3,770,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥270,000)
Fiscal Year 2007: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2006: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
We investigated the effect of carcinogenic metal cadmium (Cd) on splicing machinery. As Cd induces various kinds of gene expressions including splicing-related proteins and changes activities of Zn-finger proteins by substitution of Zn, it is supposed that exposure to this metal may disrupt the splicing reaction. We also assessed the effects of Cd on the induction of homeobox genes which are associated with carcinogenesis.
1. We exposed Cd to fibroblast cells derived from an SMA type I patient, and measured the expression level of exon 7-excluded mRNA (Δ7-SMN) using RT-PCR. Exposure to 30-100μM CdCl_2 increased the level of Δ7-SMN by 2.5-fold. The result suggests that Cd may disrupt the splicing reaction of SMN gene. In addition, Cd exposure increased ZNF265 mRNA expression by 1.6-fold. As ZNF265 was reported to regulate the alternative splicing, it seems possible that the induction of ZN265 by Cd exposure affects the increase of Δ7-SMN.
2. Cd exposure did not induce splice variants of BRCA1 and BRCA2 genes in MCF-7 cells, however, 50μM Cd significantly decreased mRNA expressions of both genes. As these genes are known as tumor suppressor genes, reduced expression may be involved in the carcinogenic mechanism of Cd.
3. We assessed the effects of Cd on the expression levels of homeobox genes, which are associated with carcinogenesis. Among 6 homeobox genes examined in this study, only HOXB8 exhibited increased mRNA expression (5.4-fold) in COS-7 cells treated with 10gM CdCl_2. The levels of HOXA7, A9, C4, C9 and C10 mRNAs decreased by 0.1-0.3-fold. Silencing of HOXB8 mRNA expression using a siRNA increased HOXC9 and C10 mRNA expression levels by 6.6- and 1.9-fold, respectively. These results suggest that HOXB8 upregulation is associated with suppression of HOXC9 and C10, and that decreased expression of HOXC9 and C10 after Cd exposure is partly due to HOXB8 induction.
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