1. RecQ helicases in the malaria parasite Plasmodium falciparum affect genome stability, gene expression patterns and DNA replication dynamics
- Author
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Claessens, Antoine, Harris, Lynne M., Stanojcic, Slavica, Chappell, Lia, Stanton, Adam, Kuk, Nada, Veneziano-Broccia, Pamela, Sterkers, Yvon, Rayner, Julian C., Merrick, Catherine J., Maladies infectieuses et vecteurs : écologie, génétique, évolution et contrôle (MIVEGEC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), London School of Hygiene and Tropical Medicine (LSHTM), Medical Research Council Unit The Gambia (MRC), Keele University [Keele], Biologie, Génétique et Pathologie des Pathogènes Eucaryotes (MIVEGEC-BioGEPPE), Pathogènes, Environnement, Santé Humaine (EPATH), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Maladies infectieuses et vecteurs : écologie, génétique, évolution et contrôle (MIVEGEC), Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), University of Cambridge [UK] (CAM), Claessens, Antoine [0000-0002-4277-0914], Harris, Lynne M [0000-0001-7310-8504], Stanton, Adam [0000-0003-3865-2381], Veneziano-Broccia, Pamela [0000-0002-3498-7304], Rayner, Julian C [0000-0002-9835-1014], Merrick, Catherine J [0000-0001-7583-2176], and Apollo - University of Cambridge Repository
- Subjects
DNA Replication ,Plasmodium ,Chromosome Structure and Function ,Plasmodium falciparum ,DNA transcription ,Protozoan Proteins ,Antigens, Protozoan ,QH426-470 ,Research and Analysis Methods ,Biochemistry ,Genomic Instability ,Chromosomes ,Evolution, Molecular ,[SDV.BBM.GTP]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Genomics [q-bio.GN] ,Parasite Groups ,Genetics ,Humans ,[SDV.MP.PAR]Life Sciences [q-bio]/Microbiology and Parasitology/Parasitology ,Malaria, Falciparum ,Molecular Biology Techniques ,QH426 ,Molecular Biology ,Protozoans ,[SDV.GEN.GPO]Life Sciences [q-bio]/Genetics/Populations and Evolution [q-bio.PE] ,RecQ Helicases ,Whole Genome Sequencing ,Chromosome Biology ,Gene Expression Profiling ,Organisms ,Malarial Parasites ,Biology and Life Sciences ,Proteins ,Eukaryota ,DNA ,Cell Biology ,Parasitic Protozoans ,Enzymes ,Nucleic acids ,Telomeres ,Gene Expression Regulation ,Gene Knockdown Techniques ,Enzymology ,Helicases ,Parasitology ,Gene expression ,Apicomplexa ,RNA, Protozoan ,Research Article ,Cloning - Abstract
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. The molecular factors controlling the inconsistent stability of this genome are not known. Here we studied the roles of the two putative RecQ helicases in P. falciparum, PfBLM and PfWRN. When PfWRN was knocked down, recombination rates increased four-fold, generating chromosomal abnormalities, a high rate of chimeric var genes and many microindels, particularly in known ‘fragile sites’. This is the first identification of a gene involved in suppressing recombination and maintaining genome stability in Plasmodium. By contrast, no change in mutation rate appeared when the second RecQ helicase, PfBLM, was mutated. At the transcriptional level, however, both helicases evidently modulate the transcription of large cohorts of genes, with several hundred genes—including a large proportion of vars—showing deregulated expression in each RecQ mutant. Aberrant processing of stalled replication forks is a possible mechanism underlying elevated mutation rates and this was assessed by measuring DNA replication dynamics in the RecQ mutant lines. Replication forks moved slowly and stalled at elevated rates in both mutants, confirming that RecQ helicases are required for efficient DNA replication. Overall, this work identifies the Plasmodium RecQ helicases as major players in DNA replication, antigenic diversification and genome stability in the most lethal human malaria parasite, with important implications for genome evolution in this pathogen., Author summary Human malaria is caused by Plasmodium parasites, with most of the mortality (almost half a million deaths each year) being caused by one species, Plasmodium falciparum. This parasite has an unusual genome: it is exceptionally biased towards A and T nucleotides rather than G and C, and it contains specific areas rich in hypervariable virulence-associated genes which evolve very rapidly to produce new variants. This evolution is probably vital for the parasite to evade the human immune system and maintain chronic infections, but how it is controlled at a molecular level remains unknown. We have identified a helicase in the parasite with a huge influence on genome stability and the rate of genome evolution. It appears to function by unwinding various unusual DNA structures, and if this fails then the genome becomes unstable. In addition, the transcription of many genes whose DNA tends to form secondary structures is affected, and DNA replication is impeded. If this helicase was expressed variably in different parasite strains infecting humans, it could influence the parasites’ ability to grow and replicate efficiently, and also, crucially, its ability to evolve and thus evade the human immune system.
- Published
- 2018