Human p68 kinase exhibits growth suppression in yeast and homology to the translational regulator GCN2.
The human p68 kinase is an interferon-regulated enzyme that inhibits protein synthesis when activated by double-stranded RNA. We show here that when expressed in Saccharomyces cerevisiae, the p68 kinase produced a growth suppressing phenotype resulting from an inhibition of polypeptide chain initiation consistent with functional protein kinase activity. This slow growth phenotype was reverted in yeast by two different mechanisms: expression of the p68 kinase N-terminus, shown to bind double-stranded RNA in vitro and expression of a mutant form of the alpha-subunit of yeast initiation factor 2, altered at a single phosphorylatable site. These results provide the first direct in vivo evidence that the p68 kinase interacts with the alpha-subunit of eukaryotic initiation factor 2. Sequence similarity with a yeast translational regulator, GCN2, further suggests that this enzyme may be a functional homolog in higher eukaryotes, where its normal function is to regulate protein synthesis through initiation factor 2 phosphorylation.
Chong
K L
KL
Research Institute, Hospital for Sick Children, Toronto, Canada.
Feng
L
L
Schappert
K
K
Meurs
E
E
Donahue
T F
TF
Friesen
J D
JD
Hovanessian
A G
AG
Williams
B R
BR
D000595:Amino Acid Sequence; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D006801:Humans; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010957:Plasmids; D011132:Polyribosomes / Q000201:enzymology; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid; D013489:Suppression, Genetic; D014157:Transcription Factors / Q000235:genetics*; D019892:eIF-2 Kinase
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D011494:Protein Kinases; D019892:eIF-2 Kinase