2005 Fiscal Year Final Research Report Summary
Development of therapeutic agents for leukemia that are targeted to a novel message originated from CREB gene
| Project/Area Number |
16590969
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Hematology
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| Research Institution | International Medical Center of Japan (Research Institute) |
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Principal Investigator |
SAEKI Kumiko Research Institute International Medical Center of Japan, Division of Hematopoietic Disorder, Department of Hematology, Division Chief, 血液疾患研究部・造血障害研究室, 室長 (80322717)
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| Project Period (FY) |
2004 – 2005
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| Keywords | CREB / fusion message / Alu / leukemic cell / poly A signal / histone acetylation / histone acetylation / CHIP assay |
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| Research Abstract |
We previously reported that 1) antisense oligodeoxyribonucleotides against cyclic AMP response element-binding protein (AS-CREB) induced deaths of leukemic but not of normal hematopoietic cells and 2) AS-CREBs failed in reducing the CREB message expression although they induced leukemic cell death in a hybridization-dependent manner. We hypothesized that there should be a genuine target message of AS-CREB other than a canonical CREB message. Here we identified a novel CREB message, where the exon 2 was fused with an Alu element in the intron 4 in a splicing-independent manner. The expression of this fusion message was quite low and it was effectively eliminated by AS-CREB. Down-regulation of the fusion message either by an antisense message introduction or a fusion point-targeting siRNA treatment eventually caused leukemic cell death. Interestingly, AS-CREBs were ineffective in eliminating the fusion message in normal cells, compatible to their resistance to AS-CREB-mediated cell death, by unknown reasons. We propose that an atypical splicing-independent CREB fusion message is a genuine target of AS-CREBs during leukemic cell death. In regard to the 3' end of the fusion message, we identified that the fusion message uses the third consensus poly A signal site in the intron 4. We then perfomed CHIP assay to determine the level of methylation and acetylation of CREB gene. The histone acetylation levels at the exon 1 were high, whereas the histone acetylation levels markedly decreased at regions covering from the exon 2 to the exon 8. The histone methylation levels were also high at exon 2 to exon 6. In addition, trichostatin A, a histone deacetylase inhibitor, inhibited the expression of the fusion message, indicating that the hypo-acetylation states at the exon 2 and its 3' downstream regions of the CREB gene is involved in the generation of the fusion message.
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