Positive regulation of jun/AP-1 by E1A

Area of Science:

• Molecular Biology
• Oncology
• Virology

Background:

• Adenovirus E1A oncogene proteins regulate viral and cellular genes.
• E1A's regulatory function is linked to modifying cellular factors interacting with promoters.

Purpose of the Study:

• To investigate the effect of adenovirus E1A oncogene expression on the jun/AP-1 transcription factor activity.
• To determine if E1A modulates signal transduction pathways, specifically those involving protein kinase C.

Main Methods:

• Assessing jun/AP-1 transcription factor activity in P19, JEG-3, and HeLa cells expressing E1A.
• Analyzing the expression of endogenous c-jun and jun B genes.
• Investigating the direct transactivation of c-fos, c-jun, and jun B promoters by E1A.
• Comparing the effects of E1A 12S and 13S products on TRE transactivation and cooperation with c-jun.

Main Results:

• E1A expression induces jun/AP-1 transcription factor binding to TPA-responsive elements (TREs) in all tested cell types.
• E1A upregulates the expression of endogenous c-jun and jun B genes.
• E1A directly transactivates the promoters of c-fos, c-jun, and jun B.
• The E1A 13S product transactivates TREs and cooperates with c-jun, while the 12S product requires c-jun cotransfection for TRE activation.
• Coexpression of c-fos with E1A 12S inhibits c-jun transactivation, highlighting fos's role.

Conclusions:

• Adenovirus E1A oncogene proteins induce jun/AP-1 transcription factor activity, impacting cellular gene regulation.
• E1A modulates signal transduction pathways potentially involving protein kinase C.
• Different E1A isoforms (12S and 13S) exhibit distinct mechanisms in TRE transactivation and interaction with c-jun and c-fos.