PubMed · 8752976
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T Hotta. 1996. [Bone marrow failure--current progress in pathophysiology].. https://pubmed.ncbi.nlm.nih.gov/8752976/
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The mode of expression of delta-aminolevulinate synthase (ALAS), as well as that of mRNAs for other heme pathway enzymes, was examined in the rat Harderian gland. Northern blot and in situ hybridization analyses demonstrated that the non-specific ALAS (ALAS-N) mRNA is highly expressed in this tissue, whereas the erythroid-specific ALAS (ALAS-E) mRNA is not. Immunoblot analysis of ALAS also confirmed this finding at the protein level. ALAS-N mRNA was maximally induced in the Harderian gland and was not increased further by treatment of animals with 2-allyl-2-isopropylacetamide (AIA). The levels of mRNAs for other heme pathway enzymes, i.e., delta-aminolevulinate dehydratase, porphobilinogen deaminase, uroporphyrinogen decarboxylase, and coproporphyrinogen oxidase, also were increased markedly in the Harderian gland and not influenced by AIA treatment. The level of ferrochelatase (FeC) mRNA in the gland was, however, lower than that in the liver. The gland contained an extremely high level of protoporphyrin, while heme was undetectable. Microsomal heme oxygenase-1 (HO-1) mRNA levels were significantly higher in the Harderian gland than in the liver. When isolated glands were incubated with hemin in vitro in organ cultures, the level of HO-1 mRNA was increased, whereas the ALAS-N mRNA level was not. These findings indicate that markedly elevated levels of protoporphyrin and extremely low levels of heme in the Harderian gland are the results of both decreased expression of FeC and markedly increased expression of ALAS-N and HO-1. The constitutive expression of the ALAS-N gene in the Harderian gland suggests a novel transcriptional control mechanism of this gene.
6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) catalyzes the synthesis and degradation of fructose-2,6-bisphosphate, a potent regulator of glycolysis. Previous studies assigned the gene for human liver PFK-2/FBPase-2 (HGMW-approved symbol PFKFB1) to the X chromosome; however, precise localization remained ambiguous, with the gene variously placed between Xcen-q13, Xq27-q28, and Xp11.22-p11.21. We have localized the gene within a YAC contig clustered around ALAS2 (human erythroid delta-aminolevulinate synthase) in Xp11.21 and have identified eight YACs positive for the gene. Four of these overlapping YACs were mapped using rare-cutter restriction enzymes to provide in-depth characterization of an 820-kb region encompassing the PFK-2/ FBPase-2 and ALAS2 genes. PFK-2/FBPase-2 was found to lie close (within approx. 250 kb) and telomeric to ALAS2. Three putative CpG islands were also detected in the region.
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