REGULATION OF PROTEIN SYNTHESIS IN RABBIT RETICULOCYTE LYSATES BY DOUBLE STRANDED RNA (dsRNA) ACTIVATED PROTEIN KINASE THAT PHOSPHORYLATES INITIATION FACTOR eIF-2

1981 ◽  
pp. 542
Author(s):  
Rajinder Singh Ranu
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Initiation Factor ◽  
Double Stranded Rna ◽  
Reticulocyte Lysates

scholarly journals Double-Stranded RNA-Activated Protein Kinase (PKR) Is Negatively Regulated by 60S Ribosomal Subunit Protein L18

1999 ◽  
Vol 19 (2) ◽  
pp. 1116-1125 ◽  
Author(s):  
Kotlo U. Kumar ◽  
Sri P. Srivastava ◽  
Randal J. Kaufman
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Cell Growth ◽  
Ribosomal Subunit ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Cancer Tissue ◽  
Double Stranded Rna ◽  
Dsrna Binding

ABSTRACT The double-stranded RNA (dsRNA)-activated protein kinase (PKR) provides a fundamental control step in the regulation of protein synthesis initiation through phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2α), a process that prevents polypeptide chain initiation. In such a manner, activated PKR inhibits cell growth and induces apoptosis, whereas disruption of normal PKR signaling results in unregulated cell growth. Therefore, tight control of PKR activity is essential for regulated cell growth. PKR is activated by dsRNA binding to two conserved dsRNA binding domains within its amino terminus. We isolated a ribosomal protein L18 by interaction with PKR. L18 is a 22-kDa protein that is overexpressed in colorectal cancer tissue. L18 competed with dsRNA for binding to PKR, reversed dsRNA binding to PKR, and did not directly bind dsRNA. Mutation of K64E within the first dsRNA binding domain of PKR destroyed both dsRNA binding and L18 interaction, suggesting that the two interactive sites overlap. L18 inhibited both PKR autophosphorylation and PKR-mediated phosphorylation of eIF-2α in vitro. Overexpression of L18 by transient DNA transfection reduced eIF-2α phosphorylation and stimulated translation of a reporter gene in vivo. These results demonstrate that L18 is a novel regulator of PKR activity, and we propose that L18 prevents PKR activation by dsRNA while PKR is associated with the ribosome. Overexpression of L18 may promote protein synthesis and cell growth in certain cancerous tissue through inhibition of PKR activity.

Regulation of protein synthesis in rabbit reticulocyte lysates: effect of of Ca2+, Mg2+, and Mn2+ on self-phosphorylation and heterophosphorylation catalyzed by the heme-regulated and double-stranded-RNA-activated protein kinases

1982 ◽  
Vol 2 (10) ◽  
pp. 813-817 ◽  
Author(s):  
Rajinder Singh Ranu
Keyword(s):  
Protein Synthesis ◽  
Cyclic Amp ◽  
Protein Kinases ◽  
Divalent Cations ◽  
The Other ◽  
Initiation Factor ◽  
Inhibitory Protein ◽  
Double Stranded Rna ◽  
Reticulocyte Lysates ◽  
Independent Protein

The influence of divalent cations Mg2+, Mn2+, and Ca2+ on the cyclic-AMP-independent protein kinases of the heine-regulated and double-stranded-RNA-activated translational inhibitory protein kinases on self-phosphorylation and heterophosphorylation of the substrate (the 38 000-dalton subunit of initiation factor eIF-2) has been examined, Results show that Mg2+, Mn2+, and Ca2+ affect the activities of these enzymes in the following fashion. Mg2+ supports both self-phosphorylation and heterophosphorylation efficiently. Mn2+ on the other hand supports self-phosphorylation but to a lesser degree the heterophosphorylation, Ca2+ promotes neither self-phosphorylation nor hetero-phosphorylation.

scholarly journals Murine Cytomegalovirus m142 and m143 Are both Required To Block Protein Kinase R-Mediated Shutdown of Protein Synthesis

2006 ◽  
Vol 80 (20) ◽  
pp. 10181-10190 ◽  
Author(s):  
Ralitsa S. Valchanova ◽  
Marcus Picard-Maureau ◽  
Matthias Budt ◽  
Wolfram Brune
Keyword(s):  
Protein Synthesis ◽  
Protein Kinase ◽  
Rna Binding ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Murine Cytomegalovirus ◽  
Deletion Mutants ◽  
Sequence Motifs ◽  
Protein Kinase R ◽  
Double Stranded Rna

ABSTRACT Cytomegaloviruses carry the US22 family of genes, which have common sequence motifs but diverse functions. Only two of the 12 US22 family genes of murine cytomegalovirus (MCMV) are essential for virus replication, but their functions have remained unknown. In the present study, we deleted the essential US22 family genes, m142 and m143, from the MCMV genome and propagated the mutant viruses on complementing cells. The m142 and the m143 deletion mutants were both unable to replicate in noncomplementing cells at low and high multiplicities of infection. In cells infected with the deletion mutants, viral immediate-early and early proteins were expressed, but viral DNA replication and synthesis of the late-gene product glycoprotein B were inhibited, even though mRNAs of late genes were present. Global protein synthesis was impaired in these cells, which correlated with phosphorylation of the double-stranded RNA-dependent protein kinase R (PKR) and its target protein, the eukaryotic translation initiation factor 2α, suggesting that m142 and m143 are necessary to block the PKR-mediated shutdown of protein synthesis. Replication of the m142 and m143 knockout mutants was partially restored by expression of the human cytomegalovirus TRS1 gene, a known double-stranded-RNA-binding protein that inhibits PKR activation. These results indicate that m142 and m143 are both required for inhibition of the PKR-mediated host antiviral response.

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