Cactin is essential for G1 progression in <i>Toxoplasma gondii</i>

Szatanek, Tomasz; Anderson-White, Brooke R.; Faugno-Fusci, David M.; White, Michael; Gubbels, Marc‐Jan

doi:10.1111/j.1365-2958.2012.08044.x

Cited by 28 publications

(31 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…First, we established at which point the normal cell division cycle derails by incubating synchronized RH and V-A15 parasites at 40˚C and staining with a centrosome (anti-HsCentrin) and budding marker (anti-TgIMC3) (Fig. 1A); we have used this marker combination in the past to determine the stage of arrested development (Szatanek et al, 2012). Parasites were synchronized by a 3-methyladenine (3-MA) block, which arrests parasites just before centrosome duplication (supplementary material Fig.…”

Section: Resultsmentioning

confidence: 99%

The Toxoplasma gondii centrosome is the platform for internal daughter budding as revealed by a Nek1 kinase mutant

Chen

Gubbels

2013

Journal of Cell Science

Self Cite

101

View full text Add to dashboard Cite

SummaryThe pathology and severity of toxoplasmosis results from the rapid replication cycle of the apicomplexan parasite Toxoplasma gondii. The tachyzoites divide asexually through endodyogeny, wherein two daughter cells bud inside the mother cell. Before mitosis is completed, the daughter buds form around the duplicated centrosomes and subsequently elongate to serve as the scaffold for organellogenesis and organelle partitioning. The molecular control mechanism of this process is poorly understood. Here, we characterized a T. gondii NIMA-related kinase (Nek) ortholog that was identified in a chemical mutagenesis screen. A temperaturesensitive mutant, V-A15, possesses a Cys316Arg mutation in TgNek1 (a novel mutant allele in Neks), which is responsible for growth defects at the restrictive temperature. Phenotypic analysis of V-A15 indicated that TgNek1 is essential for centrosome splitting, proper formation of daughter cells and faithful segregation of genetic material. In vitro kinase assays showed that the mutation abolishes the kinase activity of TgNek1. TgNek1 is recruited to the centrosome prior to its duplication and localizes on the duplicated centrosomes facing the spindle poles in a cell-cycle-dependent manner. Mutational analysis of the activation loop suggests that localization and activity are spatio-temporally regulated by differential phosphorylation. Collectively, our results identified a novel temperature-sensitive allele for a Nek kinase and highlight its essential function in centrosome splitting in Toxoplasma. Moreover, these results conclusively show for the first time that Toxoplasma bud assembly is facilitated by the centrosome because defective centrosome splitting results in single daughter cell budding.

show abstract

Section: Resultsmentioning

confidence: 99%

The Toxoplasma gondii centrosome is the platform for internal daughter budding as revealed by a Nek1 kinase mutant

Chen

Gubbels

2013

Journal of Cell Science

Self Cite

101

View full text Add to dashboard Cite

show abstract

“…To date, seven ApiAP2 proteins have been identified as regulators of stage-specific development, including liver-stage maturation (AP2-L) 71 , salivary gland sporozoite formation (AP2-Sp) 73 , ookinete development (AP2-O) 72 and gametocyte commitment (AP2-G) 47,50 in Plasmodium spp., as well as bradyzoite development (AP2IX-9 and AP2XI-4) 125,126 , virulence and host invasion (AP2XI-5) in the related apicomplexan parasite Toxoplasma gondii 127 . Many ApiAP2 proteins are also predicted to be involved in the regulation of the parasite cell cycle 75,[128][129][130][131] .…”

Section: Box 2 | Apiap2 Dna-binding Proteinsmentioning

confidence: 99%

Sexual development in Plasmodium parasites: knowing when it's time to commit

2015

View full text Add to dashboard Cite

Malaria is a devastating infectious disease that is caused by blood-borne apicomplexan parasites of the genus Plasmodium. These pathogens have a complex lifecycle, which includes development in the anopheline mosquito vector and in the liver and red blood cells of mammalian hosts, a process which takes days to weeks, depending on the Plasmodium species. Productive transmission between the mammalian host and the mosquito requires transitioning between asexual and sexual forms of the parasite. Blood- stage parasites replicate cyclically and are mostly asexual, although a small fraction of these convert into male and female sexual forms (gametocytes) in each reproductive cycle. Despite many years of investigation, the molecular processes that elicit sexual differentiation have remained largely unknown. In this Review, we highlight several important recent discoveries that have identified epigenetic factors and specific transcriptional regulators of gametocyte commitment and development, providing crucial insights into this obligate cellular differentiation process.

show abstract

“…Recent reflections on the cell cycles of fungi and animals [9], indicates we should expect regulatory factor divergence even where protozoan cell cycles appear to have preserved the same network topology working to control multicellular eukaryote division. Not surprising, all expected levels of protein conservation from pan-eukaryote to species-specific growth factors are emerging from unbiased genetic screens now successfully developed for the study of Toxoplasma gondii cell division (Suvorova and White, unpublished) [8], [10], [11].…”

Section: Introductionmentioning

confidence: 99%

Discovery of a Splicing Regulator Required for Cell Cycle Progression

et al. 2013

View full text Add to dashboard Cite

In the G1 phase of the cell division cycle, eukaryotic cells prepare many of the resources necessary for a new round of growth including renewal of the transcriptional and protein synthetic capacities and building the machinery for chromosome replication. The function of G1 has an early evolutionary origin and is preserved in single and multicellular organisms, although the regulatory mechanisms conducting G1 specific functions are only understood in a few model eukaryotes. Here we describe a new G1 mutant from an ancient family of apicomplexan protozoans. Toxoplasma gondii temperature-sensitive mutant 12-109C6 conditionally arrests in the G1 phase due to a single point mutation in a novel protein containing a single RNA-recognition-motif (TgRRM1). The resulting tyrosine to asparagine amino acid change in TgRRM1 causes severe temperature instability that generates an effective null phenotype for this protein when the mutant is shifted to the restrictive temperature. Orthologs of TgRRM1 are widely conserved in diverse eukaryote lineages, and the human counterpart (RBM42) can functionally replace the missing Toxoplasma factor. Transcriptome studies demonstrate that gene expression is downregulated in the mutant at the restrictive temperature due to a severe defect in splicing that affects both cell cycle and constitutively expressed mRNAs. The interaction of TgRRM1 with factors of the tri-SNP complex (U4/U6 & U5 snRNPs) indicate this factor may be required to assemble an active spliceosome. Thus, the TgRRM1 family of proteins is an unrecognized and evolutionarily conserved class of splicing regulators. This study demonstrates investigations into diverse unicellular eukaryotes, like the Apicomplexa, have the potential to yield new insights into important mechanisms conserved across modern eukaryotic kingdoms.

show abstract

Cactin is essential for G1 progression in Toxoplasma gondii

Cited by 28 publications

References 47 publications

The Toxoplasma gondii centrosome is the platform for internal daughter budding as revealed by a Nek1 kinase mutant

The Toxoplasma gondii centrosome is the platform for internal daughter budding as revealed by a Nek1 kinase mutant

Sexual development in Plasmodium parasites: knowing when it's time to commit

Discovery of a Splicing Regulator Required for Cell Cycle Progression

Contact Info

Product

Resources

About