Differential association of Orc1 and Sir2 proteins to telomeric domains in <i>Plasmodium falciparum</i>

Mâncio-Silva, Liliana; Rojas-Meza, Ana Paola; Vargas, Miguel; Scherf, Artur; Hernández‐Rivas, Rosaura

doi:10.1242/jcs.026427

Cited by 72 publications

(105 citation statements)

References 48 publications

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“…To find whether recombinant PfORC1C has affinity toward the telomeric region, we have performed a gel shift assay using radiolabeled probe containing the telomeric region, as described earlier (16). We find that the PfORC1C binds strongly to these regions, whereas PfORC1C Tr does not bind under the same experimental conditions (see Fig.…”

Section: Resultsmentioning

confidence: 74%

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Functional Dissection of the Catalytic Carboxyl-Terminal Domain of Origin Recognition Complex Subunit 1 (PfORC1) of the Human Malaria Parasite Plasmodium falciparum

et al. 2009

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Origin recognition complex subunit 1 (ORC1) is essential for DNA replication in eukaryotes. The deadly human malaria parasite Plasmodium falciparum contains an ORC1/CDC6 homolog with several interesting domains at the catalytic carboxyl-terminal region that include a putative nucleoside triphosphate-binding and hydrolysis domain, a putative PCNA-interacting-protein (PIP) motif, and an extreme C-terminal region that shows poor homology with other ORC1 homologs. Due to the unavailability of a dependable inducible gene expression system, it is difficult to study the structure and function of essential genes in Plasmodium. Using a genetic yeast complementation system and biochemical experiments, here we show that the putative PIP domain in ORC1 that facilitates in vitro physical interaction with PCNA is functional in both yeast (Saccharomyces cerevisiae) and Plasmodium in vivo, confirming its essential biological role in eukaryotes. Furthermore, despite having less sequence homology, the extreme C-terminal region can be swapped between S. cerevisiae and P. falciparum and it binds to DNA directly, suggesting a conserved role of this region in DNA replication. These results not only provide us a useful system to study the function of the essential genes in Plasmodium, they help us to identify the previously undiscovered unique features of replication proteins in general.Origin recognition complex subunit 1 (ORC1), the largest subunit among the ORC components is essential for DNA replication initiation in eukaryotes. ORC1 has a regulatory function in DNA replication since it comes on and off chromatin during cell cycle. Human ORC binds to chromatin during G 1 phase of the cell cycle, followed by degradation of ORC1 by a ubiquitin-mediated pathway. ORC1 reappears during M phase, and it binds to DNA at the onset of G 1 phase (21). In mammalian cells, monoubiquitination and phosphorylation may also lead to the subcellular localization of ORC1 to control DNA replication (24). In the case of Xenopus laevis, ORC1 is bound to chromatin during early interphase but it is destabilized later with the loading of MCM proteins on chromatin (23). While in Drosophila melanogaster, the level of ORC1 is developmentally regulated (2), the murine ORC1 binds to specific locus in the ribosomal RNA in a cell-cycledependent manner (29). Interestingly, in the yeast Saccharomyces cerevisiae, although ORC is tightly bound to chromatin throughout the cell cycle, another pre-replication complex (pre-RC) protein, CDC6, comes on and off chromatin, ensuring the control of DNA replication during cell cycle (7,22). The role of S. cerevisiae ORC1 (ScORC1) in ORC-DNA binding and modulating ScORC function has been described recently using highresolution electron microscopy of ScORC (5).ORC1 proteins consist of two highly conserved domains: the N-terminal regulatory domain that contains the bromo-adjacent homology domain and the C-terminal catalytic domain that contains the AAA ϩ ATPase domain. The bromo-adjacent homology domain is involved in the regulati...

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Section: Resultsmentioning

confidence: 74%

“…It has been shown recently that endogenous PfORC1 has affinity toward the telomeric region and telomere-associated repetitive elements (16). To find whether recombinant PfORC1C has affinity toward the telomeric region, we have performed a gel shift assay using radiolabeled probe containing the telomeric region, as described earlier (16).…”

Section: Resultsmentioning

confidence: 99%

Functional Dissection of the Catalytic Carboxyl-Terminal Domain of Origin Recognition Complex Subunit 1 (PfORC1) of the Human Malaria Parasite Plasmodium falciparum

et al. 2009

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“…Although individual parasite chromosomes are difficult to image by light microscopy, the staining intensity of DNA in the nucleus can yield useful clues about chromosome disposition (44,53,80). Recently, a significant amount of information about the internal organization of the parasite nucleus has become available with the use of markers for telomeres, nucleoli, centromeres, and gene-specific loci (7,27,41,43). This has the advantage of examining the chromosome structures that are currently not visible by TEM, leading to further insights into the fine details of the nuclear cycle in schizonts.…”

Section: Light Microscopy Views Of P Falciparum Blood-stage Mitosismentioning

confidence: 99%

Mitosis in the Human Malaria Parasite Plasmodium falciparum

2011

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Malaria is caused by intraerythrocytic protozoan parasites belonging to Plasmodium spp. (phylum Apicomplexa) that produce significant morbidity and mortality, mostly in developing countries. Plasmodium parasites have a complex life cycle that includes multiple stages in anopheline mosquito vectors and vertebrate hosts. During the life cycle, the parasites undergo several cycles of extreme population growth within a brief span, and this is critical for their continued transmission and a contributing factor for their pathogenesis in the host. As with other eukaryotes, successful mitosis is an essential requirement for Plasmodium reproduction; however, some aspects of Plasmodium mitosis are quite distinct and not fully understood. In this review, we will discuss the current understanding of the architecture and key events of mitosis in Plasmodium falciparum and related parasites and compare them with the traditional mitotic events described for other eukaryotes. SERIAL MITOSIS IS A COMMON THEME IN MALARIA PARASITE REPRODUCTIONThere are four critical points in the life cycle of Plasmodium parasites in which a small number of parasites rapidly multiply to generate much larger populations (60). These life cycle stages are male gamete development (72), sporozoite formation (5, 13), liver-stage development (68), and blood-stage asexual reproduction (9, 60). The first two of these processes occur within the mosquito vector, and the second two processes take place in the vertebrate host. During each of these Plasmodium life cycle stages, the parasites increase their numbers by using serial rounds of mitosis to create multinuclear cells and then orchestrating mass cytokinesis events to release their progeny (71). Mitosis is the process by which eukaryotic cells segregate their chromosomes in preparation for cell division (33,47,51).To create male gametes in preparation for sexual reproduction, the parasite begins with a haploid (1n) cell called a microgametocyte which is ingested by the mosquito during a blood meal (34,72). Within 12 min, this microgametocyte undergoes three rapid rounds of DNA synthesis and mitosis to generate a cell with an 8n genomic complement (35,36,73). Over the next 3 min, these genomes separate from one another and eight new haploid (1n) male gametes begin to assemble from the surface of the original cell (4, 69, 71).Within the mosquito midgut, a small number of the male gametes will fuse with female gametes that have also developed in this compartment, and this fusion will create diploid (2n) zygotes (15). These zygotes develop into motile ookinetes (4n) (36) that ultimately become embedded in the basal lamina beneath the midgut epithelial wall as oocysts (14). Over the course of several days, a single oocyst undergoes 10 to 11 rounds of DNA synthesis and mitosis to create a syncytial cell (sporoblast) with thousands of nuclei (61,70,82). In a massive cytokinesis event, thousands of haploid (1n) daughter sporozoites assemble from the surface of the mother cell (61, 67), and these infective sporozo...

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“…In addition, the H3K9me3-binding protein PfHP1 is clearly localized at an electron-dense, heterochromatin-like zone of the nuclear periphery and colocalized with the telomere clusters and subtelomeric PfSir2A protein (52, 115). The telomeric clusters are apparently tethered together by proteins (104), and a protein resembling the origin-of-recognition complex 1 (Orc1) is associated with telomere clusters at the nuclear periphery (102), which might play a role in nuclear positioning of the telomeres.…”

Section: Genomic and Nuclear Organizationmentioning

confidence: 99%

Chromatin-Mediated Epigenetic Regulation in the Malaria Parasite Plasmodium falciparum

2010

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Malaria is a major public health problem in many developing countries, with the malignant tertian parasite Plasmodium falciparum causing the most malaria-associated mortality. Extensive research, especially with the advancement of genomics and transfection tools, has highlighted the fundamental importance of chromatinmediated gene regulation in the developmental program of this early-branching eukaryote. The Plasmodium parasite genomes reveal the existence of both canonical and variant histones that make up the nucleosomes, as well as a full collection of conserved enzymes for chromatin remodeling and histone posttranslational modifications (PTMs). Recent studies have identified a wide array of both conserved and novel histone PTMs in P. falciparum, indicating the presence of a complex and divergent "histone code." Genome-wide analysis has begun to decipher the nucleosome landscape and histone modifications associated with the dynamic organization of chromatin structures during the parasite's life cycle. Focused studies on malaria-specific phenomena such as antigenic variation and red cell invasion pathways shed further light on the involvement of epigenetic mechanisms in these processes. Here we review our current understanding of chromatin-mediated gene regulation in malaria parasites, with specific reference to exemplar studies on antigenic variation and host cell invasion.Malaria continues to be a major cause of mortality and morbidity in tropical countries, bringing a death toll of ϳ1 million each year. Four human parasites (Plasmodium falciparum, P. vivax, P. malariae, and P. ovale) and a monkey parasite (P. knowlesi) have been found to infect humans naturally. P. falciparum causes the malignant form of malaria and is responsible for most malaria-associated human deaths. Intensified research in the past decade has greatly improved our understanding of the parasites and the disease they cause, especially with the sequencing of multiple parasite genomes. A striking finding from global microarray analyses of parasite gene expression is the tightly regulated transcription program during the parasite's life cycle, with genes expressed in a "just-in-time" manner (12, 93). Bioinformatic analysis has recognized a general conservation of the basal transcription machinery (15), but the scarcity of recognizable specific transcription factors in the parasite genome has led to speculation about the existence of a divergent transcription mechanism used by the malaria parasites (2, 25). However, this speculation may be inaccurate, as recent studies revealed the presence of the AP2 family of transcription factors (4, 35), which have undergone lineagespecific expansion in apicomplexan parasites (75). Nevertheless, the full complement of chromatin-modifying proteins encoded in apicomplexan parasite genomes underlines the significance of epigenetic mechanisms in transcription regulation (2,66,75,140). While epigenetic mechanisms are being intensively studied in model eukaryotes, only recently have they been explored in the m...

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Differential association of Orc1 and Sir2 proteins to telomeric domains in Plasmodium falciparum

Cited by 72 publications

References 48 publications

Functional Dissection of the Catalytic Carboxyl-Terminal Domain of Origin Recognition Complex Subunit 1 (PfORC1) of the Human Malaria Parasite Plasmodium falciparum

Functional Dissection of the Catalytic Carboxyl-Terminal Domain of Origin Recognition Complex Subunit 1 (PfORC1) of the Human Malaria Parasite Plasmodium falciparum

Mitosis in the Human Malaria Parasite Plasmodium falciparum

Chromatin-Mediated Epigenetic Regulation in the Malaria Parasite Plasmodium falciparum

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