Protein interactions of Magnaporthe oryzae protein kinase CK2 and secondary data analysis of a large number of transcriptomes suggest chaperone-like activity is integral to its function

Abstract

CK2, a serine/threonine (S/T) kinase present in eukaryotic cells is known to have a vast number of substrates. We have recently shown that it localizes to nuclei and at pores between hyphal compartments in M. oryzae. We performed a pulldown-proteomics of M. oryzae CK2 catalytic subunit MoCKa to detect interacting proteins. The MoCKa pulldown was enriched for septa and nucleoli proteins and intrinsically disordered proteins (IDPs) containing a CK2 phosphorylation motif proposed to destabilize and unfold alpha helixes. This points to a function for CK2 phosphorylation and corresponding phosphatase dephosphorylation in the formation of functional protein-protein aggregates and protein-RNA/DNA binding. To test this as widely as possible we used secondary data downloaded from databases from a large range of M. oryzae experiments and also for a relatively closely related plant pathogenic fungus, Fusarium graminearum. We found that CKa expression was strongly positively correlated with S/T phosphatases as well as with disaggregase (HSP104, YDJ1, SSA1) and an autophagy indicating protein (ATG8). The latter points to increased protein aggregate formation at high levels of CKa expression. Our results suggest a general role for CK2 in aggregation and disaggregation of IDPs and their binding to proteins, DNA and RNA interactions.