Regulation of the ferritin heavy-chain homologue gene in the yellow fever mosquito, Aedes aegypti.

In the yellow fever mosquito Aedes aegypti, the ferritin heavy-chain homologue (HCH) gene is induced by blood feeding. This suggests that ferritin may serve as a cytotoxic protector against the oxidative challenge of the blood meal and may be essential for the survival of the insect. In this study, various cis-acting elements for the gene were identified and mapped. Transfection assays showed that the strength and activity of a subset of these elements are orientation-dependent. The shift observed for the ferritin HCH cis-acting elements is unique among known ferritin genes. DNase I footprinting data together with Transfac analyses identified a number of putative sites known for their involvement in developmental and cell proliferation processes.

The ferritin light-chain homologue promoter in Aedes aegypti.

Promoters that direct the expression of antipathogenic molecules to primary sites of pathogenic invasions provide a means to interfere with these invasions. Thus, they have the potential to be used in mosquito control. However, exogenous elements are known to lower the fitness of most insects, and given the ability of insects to evolve rapidly, all currently known promoters could be rendered useless. As transgenic mosquitoes may be a major component in the fight against mosquito-borne diseases, the identification of new mosquito promoters is needed. The promoter of the Aedes aegypti ferritin light-chain homologue (LCH) gene, a gene whose expression is induced in gut tissues during blood feeding has been identified and mapped. Transfection data indicate that the ferritin LCH promoter is a strong promoter. DNase I footprinting data and Transfac analyses suggest that the ferritin LCH promoter contains putative GATA, E2F, NIT2, TATA and DPE sites. These data together provide the first detailed map of a known ferritin LCH gene.

Identification and mapping of the promoter for the gene encoding the ferritin heavy-chain homologue of the yellow fever mosquito Aedes aegypti.

Mosquitoes are responsible for the transmission of numerous human diseases. The recent development of transgenic mosquitoes provides a new tool to examine molecular interactions between insect vectors and the pathogens they transmit. One focus in generating transgenic mosquito lies on expressing anti-pathogenic proteins at primary sites of pathogenic invasions, specifically the mosquito gut. Promoters that direct the expression of anti-pathogenic proteins in the mosquito gut are thus sought after because they may provide ways to hinder pathogenic development in the mosquito. Here, we report the identification and mapping of a strong promoter from the Aedes aegypti ferritin heavy-chain homologue (HCH) gene. All known insect ferritin HCH genes are expressed in the gut and inducible by an iron overload. Our transfection assays and DNase I footprinting analyses show that the mosquito ferritin HCH-gene contains regulatory elements both upstream and downstream of the transcriptional start site. The promoter of this gene contains a CF2 site, two GATA-binding sites, an E2F site, a TATA-box, an AP-1 site and a C/EBP binding site.

Ribonucleotide reductase subunits from the yellow fever mosquito, Aedes aegypti: cloning and expression.

Ribonucleotide reductase catalyses the de novo synthesis of deoxyribonucleotides. Class I reductases use an iron center to generate a tyrosyl free radical that can initiate formation of the deoxyribonucleotide. These reductases are alpha 2 beta 2 holoenzymes, and the subunits are denoted as R1 and R2. R1 contains the allosteric binding site and the active site, whereas R2 contains a binuclear iron center that initiates formation of the tyrosyl radical. We have cloned and sequenced the cDNAs encoding the R1 and R2 subunit in the yellow fever mosquito, Aedes aegypti. The messages for these proteins are increased in response to blood-feeding.