Processing of the Epstein-Barr virus-encoded latent membrane protein p63/LMP.
We have analyzed the processing of the Epstein-Barr virus-encoded latent membrane protein (p63/LMP) in lymphoblastoid cell lines, Burkitt's lymphoma cell lines, and rodent fibroblasts transfected with the p63/LMP gene. Pulse-chase analysis by immunoprecipitation, under denaturing conditions, reveals a half-life of 2 h. This is due to turnover in the plasma membrane with cleavage of the protein, resulting in a 25,000-molecular-weight (p25) fragment derived from the carboxy-terminal portion of LMP. This fragment is rich in proline and acidic amino acids and sheds into the cytoplasm, where it appears to accumulate, being present in a six- to sevenfold molar excess over p63/LMP in immunoprecipitation analyses. p25 is, like p63/LMP, also phosphorylated (pp25) on serine and threonine residues, in the same ratio and to approximately the same extent as the intact p63/LMP molecule. Amino acid sequence analysis and carboxy-terminal labeling suggest that p25 is derived through a single cleavage adjacent to the sequence LGAPGGGPDNGPQDPD.
Moorthy
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Department of Pathology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Thorley-Lawson
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D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000032:analysis; D002472:Cell Transformation, Viral; D003593:Cytoplasm / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010766:Phosphorylation; D011487:Protein Conformation
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D008565:Membrane Proteins