Infected cell protein 34.5 (ICP-34.5, ICP34.5) is a protein expressed by the γ34.5 gene in viruses such as
herpes simplex virus; it blocks a
cellular stress response to viral infection.
It shares the C-terminal regulatory domain () with protein phosphatase 1
subunit 15A/
B.
When a cell is infected with a virus,
protein kinase R is activated by the virus'
double-stranded DNA,. Protein kinase R then
phosphorylates a protein called
eukaryotic initiation factor-2A (eIF-2A), which inactivates eIF-2A. EIF-2A is required for
translation so by shutting down eIF-2A, the cell prevents the virus from hijacking its own protein-making machinery. Viruses in turn evolved ICP34.5 to defeat the defense; it activates
protein phosphatase-1A which dephosphorylates eIF-2A, allowing translation to occur again. A herpesvirus lacking the γ34.5 gene will not be able to replicate in normal cells because it cannot make proteins.
[
The ICP34.5 deletion is useful for the construction of oncolytic herpes viruses, as cancer cells do not restrict replication as strongly.]
See also
* Viral nonstructural protein
References
Viral nonstructural proteins
{{virus-stub