The Plasmodium PI(4)K inhibitor KDU691 selectively inhibits dihydroartemisinin-pretreated Plasmodium falciparum ring-stage parasites.

Malaria control and elimination are threatened by the emergence and spread of resistance to artemisinin-based combination therapies (ACTs). Experimental evidence suggests that when an artemisinin (ART)-sensitive (K13 wild-type) Plasmodium falciparum strain is exposed to ART derivatives such as dihydroartemisinin (DHA), a small population of the early ring-stage parasites can survive drug treatment by entering cell cycle arrest or dormancy. After drug removal, these parasites can resume growth. Dormancy has been hypothesized to be an adaptive physiological mechanism that has been linked to recrudescence of parasites after monotherapy with ART and, possibly contributes to ART resistance. Here, we evaluate the in vitro drug sensitivity profile of normally-developing P. falciparum ring stages and DHA-pretreated dormant rings (DP-rings) using a panel of antimalarial drugs, including the Plasmodium phosphatidylinositol-4-OH kinase (PI4K)-specific inhibitor KDU691. We report that while KDU691 shows no activity against rings, it is highly inhibitory against DP-rings; a drug effect opposite to that of ART. Moreover, we provide evidence that KDU691 also kills DP-rings of P. falciparum ART-resistant strains expressing mutant K13.

The spiroindolone drug candidate NITD609 potently inhibits gametocytogenesis and blocks Plasmodium falciparum transmission to anopheles mosquito vector.

The global malaria agenda has undergone a reorientation from control of clinical cases to entirely eradicating malaria. For that purpose, a key objective is blocking transmission of malaria parasites from humans to mosquito vectors. The new antimalarial drug candidate NITD609 was evaluated for its transmission-reducing potential and compared to a few established antimalarials (lumefantrine, artemether, primaquine), using a suite of in vitro assays. By the use of a microscopic readout, NITD609 was found to inhibit the early and late development of Plasmodium falciparum gametocytes in vitro in a dose-dependent fashion over a range of 5 to 500 nM. In addition, using the standard membrane feeding assay, NITD609 was also found to be a very effective drug in reducing transmission to the Anopheles stephensi mosquito vector. Collectively, our data suggest a strong transmission-reducing effect of NITD609 acting against different P. falciparum transmission stages.

MEF-2 and Oct-1 bind to two homologous promoter sequence elements and participate in the expression of a skeletal muscle-specific gene.

The murine adult IIB myosin heavy chain (IIB MyHC) gene is expressed only in certain skeletal muscle fibers. Within the proximal promoter are two A + T-rich motifs, mAT1 and mAT2, which greatly enhance muscle-specific transcription; myogenic cells contain proteins that bind to these sequences. MEF-2 binds to both mAT1 and mAT2; a mutation abolishing its binding to mAT1 greatly diminishes the activity of the promoter. Both mAT motifs also form complexes with a protein requiring a target sequence typical of POU domain proteins, which migrate in electrophoretic mobility shift assays to the same position as a complex containing purified Oct-1 and which are supershifted by an antibody specific to Oct-1; this protein is therefore probably Oct-1. Footprinting experiments demonstrate that mAT1 is preferentially occupied by MEF-2 and mAT2 by Oct-1 and that these two proteins appear to bind cooperatively to their respective sites. Although the two mAT motifs have sequences that are very similar, they nonetheless exhibit distinct behaviors and perform differently in the activation of the promoter. The contribution of the IIB MyHC gene to specification of the myogenic phenotype is thus at least in part regulated by MEF-2 and Oct-1.

[Activation of transcription in eukaryotic cells: interactions between transcription factors and components of the basal transcriptional mechanism]. / Activation de la transcription chez les eucaryotes: interactions entre les facteurs de transcription et les composants de la machinerie transcriptionnelle basale]

Regulation of transcription in eucaryotes is achieved by two classes of transcription factors, GTFs (general transcription factors), which are components of the basal machinery, and sequence- and tissue-specific transcription factors. In this review, recent insights into the structure and function of components from the basal transcriptional machinery are discussed. The mechanisms of transcriptional activation involving direct interactions between trans-activators and the basal machinery are also presented.

The transcriptional activity of a muscle-specific promoter depends critically on the structure of the TATA element and its binding protein.

We have previously characterized the proximal promoter of the mouse IIB myosin heavy chain (MyHC) gene, which is expressed only in fast-contracting glycolytic skeletal muscle fibers. We show here that the substitution into this promoter of a non-canonical TATA sequence from the IgH gene results in inactivity in muscle cells, even though TATA-binding protein (TBP) can bind strongly to this mutated promoter. Chemical foot-printing data show, however, that TBP makes different DNA contacts on this heterologous TATA sequence. The inactivity of such a non-canonical TATA motif in the IIB promoter context appears to be caused by a non-functional conformation of the bound TBP-DNA complex that is incapable of sustaining transcription. The conclusions imply that the precise sequence of the promoter TATA motif needs to be matched with the specific functional class of upstream activator proteins present in a given cell type in order for the gene to be transcriptionally active.