Transcription factor AP2‐Sp and its target genes in malarial sporozoites

Abstract

SummaryThe malarial sporozoite is the stage that infects the liver, and genes expressed in this stage are potential targets for vaccine development. Here, we demonstrate that specific gene expression in this stage is regulated by an AP2-related transcription factor, designated AP2-Sp (APETALA2 in sporozoites), that is expressed from the late oocyst to the salivary gland sporozoite. Disruption of the AP2-Sp gene did not affect parasite replication in the erythrocyte but resulted in loss of sporozoite formation. The electrophoretic mobility-shift assay showed that the DNAbinding domain of AP2-Sp recognizes specific eightbase sequences, beginning with TGCATG, which are present in the proximal promoter region of all known sporozoite-specific genes. Promoter assays demonstrated that these sequences act as cis-acting elements and are critical for the expression of sporozoite-specific genes with different expression profiles. In transgenic parasites that express endogenous AP2-O (APETALA2 in ookinetes), but whose AP2 domain had been swapped with that of AP2-Sp, several target genes of AP2-Sp were induced in the ookinete stage. These results indicate that AP2-Sp is a major transcription factor that regulates gene expression in the sporozoite stage.

Global transcriptional repression: An initial and essential step for Plasmodium sexual development

“…Luciferase assays were performed by using the dual luciferase reporter assay system (Promega) according to the manufacturer's protocol. Briefly, 10 μL of infected blood was harvested from the tail and subjected to erythrocyte lysis in 0.85% NH 4 Cl. The remaining cells were lysed in 50 μL of 1× passive lysis buffer, and 20 μL of the solution was used in the assay.…”

“…To establish synchronous infections in rats, whole blood was harvested from infected rats and then cultured for 16 h. Mature schizonts were purified from the cultures with Nicodenz (Axis-Shield PoC AS) and subsequently inoculated into rats. At 19 hpi, whole blood was harvested from the rats and subjected to erythrocyte-lysis in 0.85% NH 4 Cl. To kill the asexual stages, infected mice were treated with sulfadiazine for 2 d in their drinking water.…”

“…Some members of the family are expressed in a stage-specific manner during the life cycle and play critical roles in the development of relevant stages (3)(4)(5). In asexual blood stages, this family of transcription factors is expressed in a cell cycle-specific manner (1,6), suggesting important roles in promoting the progress of this replication cycle.…”

Toxoplasma Transcription Factor TgAP2XI-5 Regulates the Expression of Genes Involved in Parasite Virulence and Host Invasion

“…The ability to recognize and bind specific DNA motifs was confirmed for a number of Plasmodium and Cryptosporidium AP2s through protein-binding microarrays using recombinant proteins encompassing their respective AP2 DNA-binding domains (9). Furthermore, two putative AP2 transcription factors of Plasmodium appear to be essential for the development of mosquito invasive stages (10) and sporozoites (11,12), and the disruption of these genes was accompanied by altered transcript profiles. In addition, genes of the ookinetes, which defines the fertilized form of the malarial parasite in a mosquito's body, formed by fertilization of a macrogamete by a microgamete and developing into an oocyst, contain a conserved TAGCTA motif in the promoters of several genes whose transcription was affected by disruption of AP2-O gene (10).…”

Epigenetics in Plasmodium: What Do We Really Know?

“…Studies in the rodent malaria species P. berghei have shown that the latter transition is regulated partly by posttranslational repression (72) and partly by a single AP2 transcription factor that activates many genes required for mosquito midgut invasion (110). It has also been shown that an AP2 factor is involved in sporozoite development (109) and that differentiation into gametocytes may be regulated by another translational repressor, PfPuf2 (36,78). These are the only two life cycle transitions for which underlying mechanisms have begun to emerge and it is not yet known whether epigenetic regulation plays a major role in any life cycle transition.…”