Adenovirus replaces mitotic checkpoint controls

Area of Science:

• Cell biology
• Virology
• Molecular biology

Background:

• Adenovirus infection triggers cellular DNA damage responses, including cell death and cell cycle arrest.
• Early adenoviral proteins E1B-55K and E4orf3 are known to inhibit DNA damage signaling pathways.
• A subset of cells infected with adenovirus mutants lacking E1B-55K and E4orf3 exhibit a mitotic-like arrest.

Purpose of the Study:

• To investigate the role of adenoviral E1B-55K and E4orf3 proteins in preventing cell cycle arrest during adenovirus infection.
• To elucidate the mechanisms by which these viral proteins regulate entry into and exit from mitosis.
• To understand the p53-dependent nature of mitotic arrest in adenovirus-infected cells.

Main Methods:

• Infection of cells with wild-type and mutant adenovirus strains (lacking E1B-55K and E4orf3).
• Cell cycle analysis to identify and quantify cells in a mitotic-like state.
• Use of colcemid to induce mitotic arrest and assess the role of viral proteins.
• Investigation of protein interactions, specifically E1B-55K with p53 and E4orf3 with cyclin B1.

Main Results:

• Adenovirus mutants lacking E1B-55K and E4orf3 predispose cells, particularly those infected early in G1, to a p53-dependent mitotic-like arrest.
• E1B-55K protein prevents inappropriate entry into mitosis, dependent on its interaction with p53.
• E4orf3 protein facilitates exit from mitosis, potentially by mislocalizing and inactivating cyclin B1.
• Expression of E4orf3 alone can overcome mitotic arrest induced by a degradation-resistant cyclin B1 variant.

Conclusions:

• Adenoviral E1B-55K and E4orf3 proteins are crucial for preventing mitotic catastrophe during infection.
• E1B-55K restricts entry into mitosis via p53 interaction, while E4orf3 promotes exit from mitosis by affecting cyclin B1.
• These viral proteins collectively ensure the infected cell does not arrest in a mitotic-like state, promoting viral replication.