Polo kinase, first identified in Drosophila over 30 years ago, is a highly conserved
enzyme that functions pleiotropically during multiple stages of cell division. Members
of this protein family have crucial roles in cell cycle progression, centriole duplication,
mitosis, cytokinesis and the DNA damage response. Although some Polo substrates
and regulatory mechanisms have been identified, we still lack complete
understanding of the cellular and molecular roles of this kinase. Previous work in the
Wakefield lab identified 40 proteins that physically interact with Polo in Drosophila
embryos, but the functional significance of these components remains unknown. As
genetic interaction screening can identify functional relationships between genes, I
performed a highly sensitive assay called Variable Dose Analysis (VDA) in
Drosophila S2R+ cells to determine which of the physical interactors also have
genetic interactions with Polo. Inhibiting Polo using the selective small-molecule
inhibitor BI-2536 and transfecting shRNA against the genes of interest allowed to
easily screen cells based on their viability phenotype. Known Polo genetic
interactors, Map205 and mtrm, were identified by the VDA screen, validating its
robustness and utility in identifying genetic interactors. Fourteen genes were
selected as hits, with components of the ubiquitination system enriched among them,
particularly all member proteins of the Skp, Cullin, F-box containing complex (SCF
complex). Six candidate polo interactors, SkpA, Cul1, slmb, Ck1α, Klp61F, and cher
were selected for validation and further characterization of the interactions in vivo.
Inhibition of Ck1α and slmb via RNAi resulted in larval lethality. Live imaging of SkpA
RNAi and Cul1 RNAi larvae showed an increase in the cortical localization of poloGFP during late anaphase/telophase. Together, these results suggest that polo may
be degraded in an SCF-dependent manner in Drosophila. Further follow up work is
needed to gain deeper insight into the relationship between the ubiquitination system
and polo.

Cells require some metals, such as zinc and manganese, but excess levels of these metals can be toxic. As a result, cells have evolved complex mechanisms for maintaining metal homeostasis and surviving metal intoxication. Here, we present the results of a large-scale functional genomic screen in Drosophila cultured cells for modifiers of zinc chloride toxicity, together with transcriptomics data for wild-type or genetically zinc-sensitized cells challenged with mild zinc chloride supplementation. Altogether, we identified 47 genes for which knockdown conferred sensitivity or resistance to toxic zinc or manganese chloride treatment, and >1800 putative zinc-responsive genes. Analysis of the 'omics data points to the relevance of ion transporters, glutathione (GSH)-related factors, and conserved disease-associated genes in zinc detoxification. Specific genes identified in the zinc screen include orthologs of human disease-associated genes CTNS, PTPRN (also known as IA-2), and ATP13A2 (also known as PARK9). We show that knockdown of red dog mine (rdog; CG11897), a candidate zinc detoxification gene encoding an ABCC-type transporter family protein related to yeast cadmium factor (YCF1), confers sensitivity to zinc intoxication in cultured cells, and that rdog is transcriptionally upregulated in response to zinc stress. As there are many links between the biology of zinc and other metals and human health, the 'omics data sets presented here provide a resource that will allow researchers to explore metal biology in the context of diverse health-relevant processes.