Effects of the G-quadruplex-binding drugs quarfloxin and CX-5461 on the malaria parasite Plasmodium falciparum.

Plasmodium falciparum is the deadliest causative agent of human malaria. This parasite has historically developed resistance to most drugs, including the current frontline treatments, so new therapeutic targets are needed. Our previous work on guanine quadruplexes (G4s) in the parasite's DNA and RNA has highlighted their influence on parasite biology, and revealed G4 stabilising compounds as promising candidates for repositioning.

A genome-wide map of DNA replication at single-molecule resolution in the malaria parasite Plasmodium falciparum.

The malaria parasite Plasmodium falciparum replicates via schizogony: an unusual type of cell cycle involving asynchronous replication of multiple nuclei within the same cytoplasm. Here, we present the first comprehensive study of DNA replication origin specification and activation during Plasmodium schizogony. Potential replication origins were abundant, with ORC1-binding sites detected every ∼800 bp.

Histone lactylation: a new epigenetic axis for host-parasite signalling in malaria?

Epigenetic modifications play important roles in the biology of malaria parasites. The new epigenetic mark histone lactylation, discovered only recently in humans, is also present in malaria parasites. It may have important functions as a key player in the epigenetic repertoire of Plasmodium.

The in vivo RNA structurome of the malaria parasite Plasmodium falciparum, a protozoan with an A/U-rich transcriptome.

Plasmodium falciparum, a protozoan parasite and causative agent of human malaria, has one of the most A/T-biased genomes sequenced to date. This may give the genome and the transcriptome unusual structural features. Recent progress in sequencing techniques has made it possible to study the secondary structures of RNA molecules at the transcriptomic level.

DNA replication dynamics during erythrocytic schizogony in the malaria parasites Plasmodium falciparum and Plasmodium knowlesi.

Malaria parasites are unusual, early-diverging protozoans with non-canonical cell cycles. They do not undergo binary fission, but divide primarily by schizogony. This involves the asynchronous production of multiple nuclei within the same cytoplasm, culminating in a single mass cytokinesis event.

GBP2 Is a Telomere-Associated Protein That Binds to G-Quadruplex DNA and RNA.

In the early-diverging protozoan parasite , few telomere-binding proteins have been identified and several are unique. telomeres, like those of most eukaryotes, contain guanine-rich repeats that can form G-quadruplex structures. In model systems, quadruplex-binding drugs can disrupt telomere maintenance and some quadruplex-binding drugs are potent anti-plasmodial agents.

G-quadruplex RNA motifs influence gene expression in the malaria parasite Plasmodium falciparum.

G-quadruplexes are non-helical secondary structures that can fold in vivo in both DNA and RNA. In human cells, they can influence replication, transcription and telomere maintenance in DNA, or translation, transcript processing and stability of RNA. We have previously showed that G-quadruplexes are detectable in the DNA of the malaria parasite Plasmodium falciparum, despite a very highly A/T-biased genome with unusually few guanine-rich sequences.

Hypnozoites in Plasmodium: Do Parasites Parallel Plants?

The phenomenon of relapsing malaria has been recognised for centuries. It is caused in humans by the parasite species Plasmodium vivax and Plasmodium ovale, which can arrest growth at an early, asymptomatic stage as hypnozoites inside liver cells. These dormant parasites can remain quiescent for months or years, then reactivate causing symptomatic malaria.

Conserved associations between G-quadruplex-forming DNA motifs and virulence gene families in malaria parasites.

Background: The Plasmodium genus of malaria parasites encodes several families of antigen-encoding genes. These genes tend to be hyper-variable, highly recombinogenic and variantly expressed. The best-characterized family is the var genes, exclusively found in the Laveranian subgenus of malaria parasites infecting humans and great apes.

Parasitic Protozoa: Unusual Roles for G-Quadruplexes in Early-Diverging Eukaryotes.

Guanine-quadruplex (G4) motifs, at both the DNA and RNA levels, have assumed an important place in our understanding of the biology of eukaryotes, bacteria and viruses. However, it is generally little known that their very first description, as well as the foundational work on G4s, was performed on protozoans: unicellular life forms that are often parasitic. In this review, we provide a historical perspective on the discovery of G4s, intertwined with their biological significance across the protozoan kingdom.

RecQ helicases in the malaria parasite Plasmodium falciparum affect genome stability, gene expression patterns and DNA replication dynamics.

The malaria parasite Plasmodium falciparum has evolved an unusual genome structure. The majority of the genome is relatively stable, with mutation rates similar to most eukaryotic species. However, some regions are very unstable with high recombination rates, driving the generation of new immune evasion-associated var genes.

ATAC-ing Transcriptional Mysteries in Malaria Parasites.

Ever since Plasmodium intraerythrocytic development was reported to proceed via an unusual "hardwired" transcriptional cascade, the control of gene transcription in malaria parasites has been an area of intense investigation. In this issue of Cell Host & Microbe, Toenhake et al. (2018) illuminate this intriguing issue by applying ATAC sequencing.

Checks and balances? DNA replication and the cell cycle in Plasmodium.

It is over 100 years since the life-cycle of the malaria parasite Plasmodium was discovered, yet its intricacies remain incompletely understood - a knowledge gap that may prove crucial for our efforts to control the disease. Phenotypic screens have partially filled the void in the antimalarial drug market, but as compound libraries eventually become exhausted, new medicines will only come from directed drug development based on a better understanding of fundamental parasite biology. This review focusses on the unusual cell cycles of Plasmodium, which may present a rich source of novel drug targets as well as a topic of fundamental biological interest.

G-Quadruplex DNA Motifs in the Malaria Parasite Plasmodium falciparum and Their Potential as Novel Antimalarial Drug Targets.

G-quadruplexes are DNA or RNA secondary structures that can be formed from guanine-rich nucleic acids. These four-stranded structures, composed of stacked quartets of guanine bases, can be highly stable and have been demonstrated to occur in the DNA of human cells and other systems, where they play important biological roles, influencing processes such as telomere maintenance, DNA replication and transcription, or, in the case of RNA G-quadruplexes, RNA translation and processing. We report for the first time that DNA G-quadruplexes can be detected in the nuclei of the malaria parasite , which has one of the most A/T-biased genomes sequenced and therefore possesses few guanine-rich sequences with the potential to form G-quadruplexes.

Plasmodium falciparum.

Plasmodium falciparum is a protozoan parasite that causes the most severe form of human malaria. Five other Plasmodium species can also infect humans - P. vivax, P.

G-Quadruplexes: Prediction, Characterization, and Biological Application.

Guanine (G)-rich sequences in nucleic acids can assemble into G-quadruplex structures that involve G-quartets linked by loop nucleotides. The structural and topological diversity of G-quadruplexes have attracted great attention for decades. Recent methodological advances have advanced the identification and characterization of G-quadruplexes in vivo as well as in vitro, and at a much higher resolution and throughput, which has greatly expanded our current understanding of G-quadruplex structure and function.

Single-molecule analysis reveals that DNA replication dynamics vary across the course of schizogony in the malaria parasite Plasmodium falciparum.

The mechanics of DNA replication and cell cycling are well-characterized in model organisms, but less is known about these basic aspects of cell biology in early-diverging Apicomplexan parasites, which do not divide by canonical binary fission but undergo unconventional cycles. Schizogony in the malaria parasite, Plasmodium, generates ~16-24 new nuclei via independent, asynchronous rounds of genome replication prior to cytokinesis and little is known about the control of DNA replication that facilitates this. We have characterised replication dynamics in P.

Recombination events among virulence genes in malaria parasites are associated with G-quadruplex-forming DNA motifs.

Background: Malaria parasites of the genus Plasmodium possess large hyper-variable families of antigen-encoding genes. These are often variantly-expressed and are major virulence factors for immune evasion and the maintenance of chronic infections. Recombination and diversification of these gene families occurs readily, and may be promoted by G-quadruplex (G4) DNA motifs within and close to the variant genes.

Transfection with thymidine kinase permits bromodeoxyuridine labelling of DNA replication in the human malaria parasite Plasmodium falciparum.

Background: Plasmodium falciparum, the causative agent of severe human malaria, is an early-diverging protozoan whose lifecycle has many unusual features, including its modes of replication. Research on the Plasmodium cell cycle, which occurs primarily via schizogony instead of canonical binary fission, has been hampered by a lack of tools and markers that can be transferred from cell cycle studies in model organisms. A common tool used to study DNA replication and the cell cycle in human cells is the labelling of newly-replicated DNA with the modified nucleotide bromodeoxyuridine (BrdU), followed by immunofluorescent detection.

Functional analysis of sirtuin genes in multiple Plasmodium falciparum strains.

Plasmodium falciparum, the causative agent of severe human malaria, employs antigenic variation to avoid host immunity. Antigenic variation is achieved by transcriptional switching amongst polymorphic var genes, enforced by epigenetic modification of chromatin. The histone-modifying 'sirtuin' enzymes PfSir2a and PfSir2b have been implicated in this process.

G-quadruplexes in pathogens: a common route to virulence control?

DNA can form several secondary structures besides the classic double helix: one that has received much attention in recent years is the G-quadruplex (G4). This is a stable four-stranded structure formed by the stacking of quartets of guanine bases. Recent work has convincingly shown that G4s can form in vivo as well as in vitro and can affect both replication and transcription of DNA.

A quantitative analysis of Plasmodium falciparum transfection using DNA-loaded erythrocytes.

Genetic modification of Plasmodium falciparum is a key molecular tool for the investigation of the biology and pathogenesis of this important human pathogen. The most effective means to introduce exogenous DNA into P. falciparum is via passive uptake following invasion into a DNA-loaded erythrocyte.

Epigenetic dysregulation of virulence gene expression in severe Plasmodium falciparum malaria.

Chronic infections with the human malaria parasite Plasmodium falciparum depend on antigenic variation. P. falciparum erythrocyte membrane protein 1 (PfEMP1), the major erythrocyte surface antigen mediating parasite sequestration in the microvasculature, is encoded in parasites by a highly diverse family of var genes.

Epigenetics in Plasmodium: what do we really know?

In the burgeoning field of Plasmodium gene expression, there are--to borrow some famous words from a former U.S. Secretary of Defense--"known knowns, known unknowns, and unknown unknowns.