Cloning and characterization of an eukaryotic initiation factor-2alpha kinase from the silkworm, Bombyx mori.
Eukaryotic initiation factor 2alpha (eIF-2alpha) kinases are involved in the translational regulations that occur in response to various types of environmental stress, and play an important role in the cellular defense system operating under unfavorable conditions. The identification of additional eIF-2alpha kinases and the elucidation of their functions are necessary to understand how different eIF-2alpha kinases can specifically respond to distinct stimuli. Here, we report a novel eIF-2alpha kinase, termed BeK, from the silkworm, Bombyx mori. This gene encodes 579 amino acids and contains all 11 catalytic domains of protein-serine/threonine kinases. Most notably, it contains an "Ile-Gln-Met-Xaa-Xaa-Cys" motif, which is highly conserved from yeast to mammalian eIF-2alpha kinases. BeK does not show any significant homology in the NH(2) terminal regulatory domain, suggesting a distinct regulatory mechanism of this novel eIF-2alpha kinase. BeK is ubiquitously expressed in the various tissues throughout the final larval stage. Importantly, BeK is activated in Drosophila Schneider cells following heat shock and osmotic stress, and activated-BeK has been shown to phosphorylate an eIF-2alpha subunit at the Ser(50) site. However, other forms of stress, such as immune stress, endoplasmic reticulum stress and oxidative stress, cannot significantly elicit BeK activity. Interestingly, the baculovirus gene product, PK2, can inhibit BeK enzymatic activity, suggesting that BeK may be an endogenous target for a viral gene product. Taken together, these data indicate that BeK is a novel eIF-2alpha kinase involved in the stress response in B. mori.
Prasad
M Dharma
MD
Laboratoire de Biochimie et Biologie Moléculaire des Insectes, Institut Pasteur, 25 rue du Dr. Roux, 75724 Cedex 15, Paris, France
Han
Sung Jun
SJ
Nagaraju
Javaregowda
J
Lee
Won Jae
WJ
Brey
Paul T
PT
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D012831:Bombyx; D002460:Cell Line; D003001:Cloning, Molecular; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009995:Osmosis; D018384:Oxidative Stress; D010766:Phosphorylation; D010802:Phylogeny; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014018:Tissue Distribution; D019892:eIF-2 Kinase / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*
D011994:Recombinant Proteins; D019892:eIF-2 Kinase