Caspase cleavage of viral proteins, another way for viruses to make the best of apoptosis

Richard, A; Tulasne, D

Adenoviruses gather more than a 100 species with about 40 being able to infect humans. Adenovirus early region 1A (AdE1A) encodes two major proteins, 12S and 13S, that are involved in the control of early viral gene expression through their interactions with the host cell machinery. In vitro, caspases 3 and 7 are able to cleave both 12S and 13S proteins, although the cleavage efficiency depends on the Caspase cleavages of viral proteins were recapitulated in tables according to the functional consequences on viral life cycle they were shown or suggested to exert. The name of the virus, nature of its genome and caspase(s) induced on infection are indicated. The characteristics of the cleavages were also summarized, with identity of the cleavage site(s), caspase(s) able to cleave in vitro and/or in cellulo (sometimes different from caspases induced in cells undergoing infection) and suggested functions of the caspase-related products as often as possible. Vertical black arrows indicate where cleavage occurs viral serotype. Furthermore, when apoptosis is chemically induced in AdE1A-transformed cells, AdE1A levels decrease but can be restored using a pan caspase inhibitor. 47 However, AdE1A levels remain stable on adenovirus infection despite TNFa-induced caspase activation. Thus, although AdE1A caspase cleavage is likely to occur, its existence on infection as well as its biological relevance for adenoviruses remains elusive so far. Interestingly, AdE1A-binding abilities to transcription factors such as CBP and TBP are affected by the cleavage, suggesting that it might modulate the expression of early viral genes.