Pkh1 interacts with and phosphorylates components of the yeast Gcn2/eIF2α system.
The yeast Saccharomyces cerevisiae responds to amino acid deprivation by increasing translation of the transcription factor Gcn4, which enhances expression of amino acid biosynthetic genes. Accumulation of uncharged tRNAs activates the Gcn2 protein kinase, which phosphorylates the alpha subunit of the eukaryotic initiation factor 2 (eIF2α). The resulting downregulation of eIF2 activity causes reduction of general translation and stimulation of GCN4 translation. S. cerevisiae contains three PDK1 orthologs (encoded by PKH1, PKH2 and PKH3) that have been implicated in nutrient signaling. Using heterologously expressed proteins, we demonstrate physical interaction between Pkh1 and all three subunits of eIF2 as well as Gcn2. We confirm the interaction between Pkh1 and Gcn2 by co-immunoprecipitation in yeast cell extracts and show that Pkh1 can phosphorylate Gcn2 in vitro. However, Pkh1 inactivation did not affect eIF2α-S51 phosphorylation in vivo or GCN4 translation in response to amino acid deprivation. Hence, the physiological importance of the close interactions between Pkh1 and Gcn2 or eIF2 could depend on other conditions and/or other targets of the Gcn2/eIF2 system.
Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Katholieke Universiteit Leuven, Belgium.
M
M
Kimpe
K
K
Voordeckers
J M
JM
Thevelein
G
G
Van Zeebroeck
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000172:deficiency; D016384:Consensus Sequence; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D047468:Immunoprecipitation; D010766:Phosphorylation; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity
D000596:Amino Acids; D015852:Eukaryotic Initiation Factor-2; D029701:Saccharomyces cerevisiae Proteins; D012694:Serine; D064413:3-Phosphoinositide-Dependent Protein Kinases; C512912:GCN2 protein, S cerevisiae; C118385:PKH1 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases