Cleavage of polypeptide chain initiation factor eIF4GI during apoptosis in lymphoma cells: characterisation of an internal fragment generated by caspase-3-mediated cleavage.
Polypeptide chain initiation factor eIF4GI undergoes caspase-mediated degradation during apoptosis to give characteristic fragments. The most prominent of these has an estimated mass of approximately 76 kDa (Middle-Fragment of Apoptotic cleavage of eIF4G; M-FAG). Subcellular fractionation of the BJAB lymphoma cell line after induction of apoptosis indicates that M-FAG occurs in both ribosome-bound and soluble forms. Affinity chromatography on m7GTP-Sepharose shows that M-FAG retains the ability of eIF4GI to associate with both the mRNA cap-binding protein eIF4E and initiation factor eIF4A and that the ribosome-bound form of M-FAG is also present as a complex with eIF4E and eIF4A. These data suggest that the binding sites for eIF4E, eIF4A and eIF3 on eIF4GI are retained in the caspase-generated fragment. M-FAG is also a substrate for cleavage by the Foot-and-Mouth-Disease Virus-encoded L protease. These properties, together with the pattern of recognition by a panel of antibodies, define the origin of the apoptotic cleavage fragment. N-terminal sequencing of the products of caspase-3-mediated eIF4GI cleavage has identified the major cleavage sites. The pattern of eIF4GI degradation and the possible roles of the individual cleavage products in cells undergoing apoptosis are discussed.
Bushell
M
M
Department of Biochemistry and Immunology, Cellular and Molecular Sciences Group, St George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK.
Poncet
D
D
Marissen
W E
WE
Flotow
H
H
Lloyd
R E
RE
Clemens
M J
MJ
Morley
S J
SJ
D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002051:Burkitt Lymphoma / Q000201:enzymology / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D010450:Endopeptidases / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D006801:Humans; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010442:Peptide Chain Initiation, Translational / Q000502:physiology*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D010448:Peptide Initiation Factors / Q000235:genetics / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000187:drug effects; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D014407:Tumor Cells, Cultured
C113920:EIF4G1 protein, human; D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D019384:Nucleic Acid Synthesis Inhibitors; D010446:Peptide Fragments; D010448:Peptide Initiation Factors; D011500:Protein Synthesis Inhibitors; D005047:Etoposide; D004247:DNA; D003513:Cycloheximide; D010450:Endopeptidases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C088747:leader proteinase, foot-and-mouth disease virus