Differential Phosphorylation of a Regulatory Subunit of Protein Kinase CK2 by Target of @entity3446 Complex 1 Signaling and the Cdc-like Kinase XXXX .

@entity375 @entity71926 @entity71928 @entity3446 @entity25601 @entity71925 @entity71927
Transcriptional regulation of ribosome and tRNA synthesis plays a central role in determining protein synthetic capacity and is tightly controlled in response to nutrient availability and cellular stress. In @entity375 , the regulation of ribosome and tRNA synthesis was recently shown to involve the Cdc-like kinase @entity71925 and the GSK-3 kinase Mck1. In this study, we explored additional roles for these conserved kinases in processes connected to the target of @entity3446 complex 1 (TORC1). We conducted a synthetic chemical-genetic screen in a @entity71925   mck1   strain and identified many novel @entity3446 -hypersensitive genes. Gene ontology analysis showed enrichment for TORC1-regulated processes (vesicle-mediated transport, autophagy, and regulation of cell size) and identified new connections to protein complexes including the protein kinase CK2. CK2 is considered to be a constitutively active kinase and in budding @entity375 , the holoenzyme comprises two regulatory subunits, @entity71926 and @entity71927 , and two catalytic subunits, @entity71928 and @entity25601 . We show that @entity71926 is differentially phosphorylated in vivo and that @entity71925 mediates this phosphorylation when nutrients are limiting and under all tested stress conditions. We determined that the phosphorylation of @entity71926 does not detectably affect the stability of the CK2 holoenzyme but correlates with the reduced occupancy of @entity71926 on tRNA genes after @entity3446 treatment. Thus, the differential occupancy of tRNA genes by CK2 is likely to modulate its activation of RNA polymerase III transcription. Our data suggest that TORC1, via its effector kinase @entity71925 , may regulate the association of CK2 with some of its substrates by phosphorylating @entity71926 .
