Novel CRK-Cyclin Complex Controls Spindle Assembly Checkpoint in Toxoplasma Endodyogeny

Abstract

The rate of Toxoplasma tachyzoite division directly correlates with the severity of the disease, toxoplasmosis, which affects humans and animals. Thus, a better understanding of the tachyzoite cell cycle would offer much-needed efficient tools to control the acute stage of infection.

Restriction Checkpoint Controls Bradyzoite Development in Toxoplasma gondii

“…We found that in addition to interaction with TgCycP1 and TgCycP2, TgCrk2 myc kinase formed a specific complex with the atypical cyclin TgCyc5 (TGME49_293280) ( Fig. 1D ) ( 22 ). While interaction with TgCycP1 and TgCycP2 may have been attributed to the presence of tachyzoites and early-stage bradyzoites, the TgCrk2/TgCyc5 complex was formed only under bradyzoite-induction conditions.…”

“…1D ). Analysis of developmentally competent ME49 tachyzoites revealed that TgCrk2 kinase formed an equivalent complex with another P-cyclin TgCycP2 (TGME49_305330) ( 22 ). To find out whether the TgCrk2 cyclin partners change during bradyzoite development, TgCrk2 myc complexes were isolated from the ME49 strain that was grown for 3 days under alkaline conditions.…”

“…P-cyclins are typically encoded in multiple copies and are known to regulate processes, such as cell cycle progression and environmental sensing. In contrast, apicomplexan parasites retained a small repertoire of P-cyclins: a single gene in haemosporidian and piroplasmids, two genes in Coccidian genera, and multiple P-cyclin genes in cryptosporidia (Table S3) ( 22 , 23 ). To define the phylogenetic relationships of apicomplexan P-cyclins, we analyzed representative factors in the Apicomplexa phylum, kinetoplastids, and ancestral alveolate Chromerids, and compared them to fungi and land plant P-cyclins ( Fig.…”

“…3D and Table S1; single centrosome), suggesting that TgCycP2 emerges in the mid-G 1 phase. The centrocone, an intranuclear compartment for the spindle, is formed in the late G 1 stage, expanded in S-phase, and is duplicated in mitotic anaphase ( 22 , 33 , 35 , 37 ). We established that TgCycP2 was downregulated in mitosis and budding stages because tachyzoites with a duplicated centrocone (α-MORN1) or with internal buds (α-IMC1) expressed significantly less TgCycP2 AID-HA ( Fig.…”

“…We recently demonstrated that the tachyzoite G 1 phase has a definitive stop regulated by atypical Cdk-related kinase TgCrk2 and noncanonical P-type cyclin TgCycP1 (formerly called TgPHO80) ( 21 ). Here, we showed that in addition to TgCycP1 (TGME49_267580), kinase TgCrk2 forms complexes with atypical cyclins TgCycP2 (TGME49_305330) and TgCyc5 (TGME49_293280) ( 21 – 23 ). The role of the novel TgCycP2 and TgCyc5 cyclins was examined in the developmentally incompetent RH and competent ME49 strains.…”