Abstract
Leishmania species are protozoan parasites whose remarkably plastic genome limits the establishment of effective genetic manipulation and leishmaniasis treatment. The strategies used by Leishmania to maintain its genome while allowing variability are not fully understood. Here, we used DiCre-mediated conditional gene deletion to show that HUS1, a component of the 9–1–1 (RAD9-RAD1-HUS1) complex, is essential and is required for a G2/M checkpoint. By analyzing genome-wide instability in HUS1 ablated cells, HUS1 is shown to have a conserved role, by which it preserves genome stability and also a divergent role, by which it promotes genome variability. These roles of HUS1 are related to distinct patterns of formation and resolution of single-stranded DNA and γH2A, throughout the cell cycle. Our findings suggest that Leishmania 9–1–1 subunits have evolved to co-opt canonical genomic maintenance and genomic variation functions. Hence, this study reveals a pivotal function of HUS1 in balancing genome stability and transmission in Leishmania. These findings may be relevant to understanding the evolution of genome maintenance and plasticity in other pathogens and eukaryotes.
Highlights
Leishmaniases are a group of life-threatening and disfiguring diseases that are globally widespread [1]
To comprehensively investigate the HUS1 function in L. major, we generated a HUS1Flox cell line in which expression of DiCre allows for conditional knockout (KO) of HUS1 flanked by LoxP sites upon rapamycin (RAP) induction [19] (Figure 1A–C)
These data demonstrate that HUS1 is pivotal for the replication stress response and plays essential roles in L. major promastigotes that cannot be supplied by RAD9 and/or RAD1 alone
Summary
Leishmaniases are a group of life-threatening and disfiguring diseases that are globally widespread [1] These neglected infections are caused by intracellular protozoan parasites of the genus Leishmania. In Leishmania species genome plasticity appears to be genome-wide, including gene amplification and chromosome copy number variation, which are hallmarks of genome instability and normally considered detrimental [4,5]. Such remarkable genome plasticity can affect the parasite’s gene expression, potentially allowing environmental adaptation [6,7], and has been shown to underlie distinct mechanisms of drug resistance, hampering the establishment of effective antileishmanial chemotherapy [8]. Genome plasticity hinders genetic manipulation of the parasite, making the understanding of its biology even more challenging
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