Evidence for an adenovirus type 2-coded early glycoprotein

Area of Science:

• Virology
• Molecular Biology
• Glycobiology

Background:

• Adenovirus type 2 (Ad2) infections involve complex interactions between viral and host cell proteins.
• Understanding early viral gene products is crucial for deciphering viral replication and pathogenesis.

Purpose of the Study:

• To identify and characterize early viral glycopolypeptides induced by adenovirus type 2 infection.
• To determine the origin (viral vs. cellular) and cellular localization of the identified glycopolypeptide.

Main Methods:

• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for molecular weight estimation.
• In vivo labeling with radioactive glucosamine and methionine.
• Concanavalin A-Sepharose affinity chromatography to assess glycosylation.
• Pulse-chase experiments to study protein modification.
• Partial proteolysis to compare polypeptide structures.
• Cellular fractionation to determine protein localization.
• Immunoprecipitation using antisera against Ad2-transformed cells.

Main Results:

• An early Ad2-induced glycopolypeptide (20/21K) was identified with an apparent molecular weight of 20-21 kDa.
• The 20/21K polypeptide was shown to be glycosylated and localized primarily in the cytoplasm.
• Pulse-chase experiments revealed post-translational modifications, suggesting glycosylation/deglycosylation.
• Partial proteolysis indicated structural similarity between the 20/21K polypeptide and a related 44K polypeptide, suggesting the latter might be a dimer.
• The 20/21K polypeptide was induced in Ad2-infected human, monkey, and hamster cells, and in some Ad2-transformed rat cells.

Conclusions:

• The 20/21K polypeptide is synthesized in Ad2-infected cells of various species.
• Evidence strongly suggests the 20/21K polypeptide is virus-coded, not host-cell-induced.
• The findings contribute to understanding early adenovirus protein synthesis and potential roles in infection.