Structure of the human ferrochelatase gene

Abstract

We have determined the structure of the human ferrochelatase gene after isolation and characterization of lambda phage clones mapping discrete regions of the cDNA. This gene was assigned to human chromosornc 18 at region q21.3, by fluorescent in situ hybridization. The gene contains a total of 11 exons and has a minimum size of about 45 kb. The exonlintron boundary sequences conform to consensus acceptor (GTn) and donor (nAG) sequences, and the exons in the gene appear to encode functional protcin domains. A major site of the transcription initiation, determined by S1 nuclease mapping, was assigned to an adcnine base 89 bases upstream from the adenine base of the translation initiation ATG. The promoter region contains a potential binding site for Spl, NF-E2 and erythroidspecific transcriptional factor GATA-1, but not a typical TATAA or CCAAT sequence. Analysis of primer extension showed that the transcription starts at the same position between hepatoma HepG2 and erythroleukemia K562 cell mRNA, thereby suggesting that there can be a single transcript in erythroid and non-erythroid cells.Ferrochelatase (protoheme lerro-lyase) is the terminal enzyme of the heme biosynthetic pathway and catalyzes the insertion of fcrrous ion into protoporphyrin 1X to form protoheme. The enzyme is located in the innermembrane ofmilochondria of various tissues including liver [l, 21, heart [3], kidney [4] and erythroid cells [4, 51. A genetic ferrochelatase deficiency in infants results in crythropoietic protoporphyria with excessive accumulation and excretion of protoporphyrin [6]. Protoporphyria in humans is a dominantly inherited disease. The enzyme activity decreases to about 50% compared with normal levels in all tissues and isolated cell preparations, including bone marrow [7], liver [8] and cultured skin fibroblasts [9]. The molecular basis of the defect has apparently not been reported.Regulation of the heme synthetic pathway differs between erythroid and non-erythroid cells. In liver and non-erythroid tissues, the rate of heme synthesis is controlled by the levcl of the first pathway enzyme, 5-aminolevulinic-acid synthase [6]. In differentiating erythroid cells, a different type of 5-aminolevulinic-acid synthase is present and cannot be ratelimiting for heme production [lo]. It has been shown that hemc synthesis increased when mouse erythroleukemia cells were induced to differentiate to cells producing hemoglobin, C'orrespondence to S. Taketani,

Identification of FECH gene multiple variations in two Chinese patients with erythropoietic protoporphyria and a review

“…The human FECH gene is located on chromosome 18q21.3 with 11 exons and 10 introns (Taketani et al, 1992) and has two transcripts which share the same functional region. The secondary structure of the FECH protein contains 17 α-helices (α 1 -α 17 ), 8 β-sheets (β 1 -β 8 ), 4 iron-sulfur cluster (2Fe-2S) binding sites, and also two active sites (Al-Karadaghi et al, 1997;Wu et al, 2001;Balwani et al, 2013).…”

Novel Null-Allele Mutations and Genotype-Phenotype Correlation in Argentinean Patients with Erythropoietic Protoporphyria

“…The human FECH gene was cloned, sequenced, and mapped to the long arm of chromosome 18 (5,6). The gene contains a total of 11 exons and spans about 45 kb of genomic DNA.…”

Successful therapeutic effect in a mouse model of erythropoietic protoporphyria by partial genetic correction and fluorescence-based selection of hematopoietic cells

“…[8][9][10] Following the cloning of the human ferrochelatase cDNA, several mutations have been identified showing a high molecular heterogeneity. [8][9][10][11][12][13] The pathophysiology of the human disease is still unclear, particularly with respect to the development of liver failure.…”