Adenovirus 2 Ip+ locus codes for a 19 kd tumor antigen that plays an essential role in cell transformation

Area of Science:

• Molecular biology
• Virology
• Cell biology

Background:

• Adenovirus 2 large plaque (Ip) mutants form large clear plaques on human KB cells.
• These mutants exhibit defects in inducing transformation of rat embryo cell line 3Y1.
• The transforming early gene block E1b (map position 4.5-11.2) encodes 53 kd and 19 kd T antigens.

Purpose of the Study:

• To investigate the role of Adenovirus 2 large plaque (Ip) mutants in cell transformation.
• To localize the Ip mutation within the E1b transforming gene block.
• To analyze the specific mutational defects in the 19 kd tumor antigen and their impact on transformation.

Main Methods:

• Marker transfer to localize the Ip mutation within the E1b gene block.
• DNA sequence analysis of Ip mutants (Ip3 and Ip5).
• Analysis of viral E1 proteins in affected mutants.

Main Results:

• Ip mutations were localized to the 19 kd tumor antigen coding region within the E1b block.
• Mutant Ip3 showed a single base pair change at the N-terminus of the 19 kd polypeptide, altering alanine to valine.
• Mutant Ip5 had two mutations: one altering aspartic acid to tyrosine near the N-terminus, and another extending the 19 kd polypeptide by changing a stop codon.

Conclusions:

• Direct genetic evidence confirms the essential role of the 19 kd tumor antigen in Adenovirus 2-induced cell transformation.
• The N-terminal region of the 19 kd tumor antigen is critical for its function in inducing cell transformation.
• Specific alterations in the 19 kd antigen, including N-terminal changes and size modification, impair its transforming activity.