| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2001: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
In the squirrel family, the genes for hibernation-specific protein, HP-20, 25 and -27, can be detected, not only in hibernating species (chipmunk and ground squirrel), but also in a nonhibernating species (tree squirrel). However, their expression is limited to the hibernating species. In this study, to reveal the molecular mechanisms underlying the liver-specific transcription of the chipmunk HP-20, -25 and -27 genes, and the causes for the abortion of expression of the corresponding genes in tree squirrel, the genomic clones for the chipmunk HP-20, -25 and -27 genes and tree squirrel HP-25 and -27 genes were isolated, and their gene structures and promoter activities were analyzed.
The chipmunk HP-20, -25 and -27 genes share conserved gene structures, and are considered to be generated by gene duplication. For the chipmunk HP-25 gene, the 80 bp 5' upstream sequence is necessary for its liver-specific transcription, and HNF-4 which binds to the sequence from -75 to -46 plays an important role. On the other hand, the tree squirrel HP-25 gene has a mutation in the HNF-4 binding site, resulting in the abortion of HNF-4 binding, which was considered to be the major cause for the lack of HP-25 expression. For the chipmunk HP-20 gene, the 57 bp 5' upstream sequence is necessary for its liver-specific transcription, and HNF-1 which binds to the sequence from -52 to -26 plays an important role. For the chipmunk HP-27 gene, the 160 bp 5' upstream sequence is necessary for its liver-specific transcription, and when the sequence from -160 to -130 was replaced with the corresponding tree squirrel sequence, almost no promoter activity was observed.
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