Expression of ferrochelatase mRNA in erythroid and non-erythroid cells

Abstract

Ferrochelatase, which catalyses the last step in haem biosynthesis, i.e. the insertion of Fe(II) into protophorphyrin IX, is present in all cells, but is particularly abundant in erythroid cells during haemoglobinization. Using mouse ferrochelatase cDNA as a probe two ferrochelatase transcripts, having lengths of 2.9 kb and 2.2 kb, were found in extracts of mouse liver, kidney, brain, muscle and spleen, the 2.9 kb transcript being more abundant in the non-erythroid tissues and the 2.2 kb transcript more predominant in spleen. In mouse erythroleukemia cells the 2.9 kb ferrochelatase transcript is also more abundant; however, following induction of erythroid differentiation by dimethyl sulphoxide there is a preferential increase in the 2.2 kb transcript, which eventually predominates. With mouse reticulocytes, the purest immature erythroid cell population available, over 90% of the total ferrochelatase mRNA is present as the 2.2 kb transcript. Since there is probably only one mouse ferrochelatase gene, the occurrence of two ferrochelatase transcripts could arise from the use of two putative polyadenylation signals in the 3' region of ferrochelatase DNA. This possibility was explored by using a 389 bp DNA fragment produced by PCR with synthetic oligoprimers having sequence similarity with a region between the polyadenylation sites. This fragment hybridized only to the 2.9 kb ferrochelatase transcript, indicating that the two transcripts differ at their 3' ends and suggesting that the 2.2 kb transcript results from the utilization of the upstream polyadenylation signal. The preferential utilization of the upstream polyadenylation signal may be an erythroid-specific characteristic of ferrochelatase gene expression.

Posttranslational stability of the heme biosynthetic enzyme ferrochelatase is dependent on iron availability and intact iron-sulfur cluster assembly machinery

“…Treatment of MEL cells with 2% DMSO induces rapid progression of MEL cells from a stage resembling late erythroid colonyforming units to a stage resembling basophilic and orthochromatophilic erythroblasts in the erythroid lineage, 35 where globin expression and hemoglobin formation are observed, along with increased expression of ferrochelatase mRNA and protein. 36 Treatment of differentiating MEL cells concomitantly with the iron chelator desferrioxamine (DFO) caused a sustained increase in IRE binding activity of IRP1 and IRP2 ( Figure 2B), whereas the differentiationinduced increase in activity of the [4Fe-4S] cluster-containing mitochondrial and cytosolic aconitases was attenuated ( Figure 2C), consistent with cellular iron depletion. Induction of Alas2 mRNA expression was observed during differentiation of MEL cells under both normal and iron-depleted conditions ( Figure 2D).…”

The Heme Biosynthesis Pathway Is Essential for Plasmodium falciparum Development in Mosquito Stage but Not in Blood Stages

“…A recent study reported successful KO of the ALAS and FC genes in the related rodent malaria parasite, P. berghei, but the authors were unable to show that these mutations ablated de novo heme synthesis (28), most likely due to background heme biosynthetic activity from the metabolically active host reticulocytes (29,30). This same study also revisited the effects of succinylacetone on the growth and heme biosynthesis activity of blood-stage P. falciparum.…”

“…Unlike P. falciparum, P. berghei parasites preferentially invade metabolically active reticulocytes, which also synthesize heme (29,30). Therefore, Nagaraj et al (28), who assessed heme biosynthesis by monitoring incorporation of [ 14 C]ALA into heme by autoradiography, were unable to show that de novo heme synthesis was disrupted in the knock-out parasites due to host cell background.…”

Molecular and genetic characterization of ferrochelatase

“…When MEL cells are induced to differentiate with DMSO, the amounts of ferrochelatase mRNA increase 5-to 6-fold by 72 h, and the size of the mRNA in the differentiated MEL cell is the same as that in mouse liver [56]. There is a recent report by Chan et al [72] showing differential induction of the two FeC mRNA in MEL cells. Northern blot analysis of rat ferrochelatase mRNA reveals that the ferrochelatase mRNA in liver is shown to be a single 2.4 kb band, and that the amount of an mRNA of the same size markedly increases in the spleen of anemic rats (unpublished observation).…”