| Project/Area Number |
04454165
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Pathological medical chemistry
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| Research Institution | Tohoku University |
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Principal Investigator |
HAYASHI Norio Tohoku University School of Medicine ; Professor, 医学部, 教授 (00004606)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAMOTO Masayuki Tohoku University School of Medicinel Associate Professor, 医学部, 講師 (50166823)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥5,800,000 (Direct Cost: ¥5,800,000)
Fiscal Year 1993: ¥2,400,000 (Direct Cost: ¥2,400,000)
Fiscal Year 1992: ¥3,400,000 (Direct Cost: ¥3,400,000)
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| Keywords | delta-aminolevulinate synthase / heme biosynthesis / gene / rat / regulatory region / δーアミノレブリン酸合成酵素 / フィードバック調節 |
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| Research Abstract |
Heme is essential for all eukaryotic cells because of its role as a prosthetic group for a number of proteins, and its intracellular concentration is highly regulated. The first and the rate-limiting step of heme biosynthesis in animals is catalyzed by delta-aminolevulinate(ALA) synthase. There are two tissue-specific isozymes of ALA synthase : the erythroid- specific ALA synthase (ALAS-E) and the non-specific ALA synthase (ALAS-N). To understand the molecular mechanisms contorolling the heme biosynthetic pathway, it is a prerequisite to analyze the structure and function of the ALA synthase genes.
We attempted isolation and characterization of the gene encoding rat ALAS-N.The ALAS-N gene was found to span more than 14kb in the rat genome, encompassing 11 exons, Analysis of the promoter region of the gene revealed several potential cos-acting regulatory elements. Comparison of the organization of rat ALAS-N gene with that of the ALAS-E gene in mouse suggests that the ancestral gene for ALA synthase in animals was probably composed of 11 exons, and both ALAS-N and ALAS-E genes were derived from this ancestral gene.
The proximal regulatory region of the human ALAS-E gene was also analyzed. The results indicated that binding sites for erythroid transcription factors are clustered within 120 bp upstream form the transcription initiation site.
RNA blot hybridization analysis was used to examine the developmental stage-specific transcription of ALAS-N and ALAS-E genes in fetal, newborn and adult rat liver. The results demonstrated that, while ALAS-E is the key enzyme which supplies large quantities of heme for hemoglobin synthesis, ALAS-N functions to supply heme to the P-450 system in the liver and also functions as a housekeeper gene to supply heme for respiratory cytochromes and other hemoproteins in various tissues.
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