Influenza A virus polymerase PB2 subunit (PB2)

The Influenza A virus polymerase PB2 subunit is a vital component of the heterotrimeric RNA-dependent RNA polymerase (RdRp) complex, which also includes the PB1 and PA subunits. Its primary biological role is to facilitate the "cap-snatching" process, where it binds the 5' methylated cap of host cellular pre-mRNAs to provide primers for viral mRNA transcription (UniProt P03428). This function makes PB2 essential for the replication cycle of the virus within host cells. Furthermore, PB2 is a major determinant of host-range restriction; specific amino acid substitutions, such as the E627K mutation, are known to enhance the replication of avian influenza viruses in mammalian hosts (NCBI PMC3400581). As a therapeutic target, PB2 has been the focus of novel antiviral development to counter resistance to neuraminidase inhibitors. Small molecules like Pimodivir (VX-787) target the highly conserved cap-binding pocket of PB2, effectively blocking the initiation of viral transcription (PubMed 24419269). While Pimodivir demonstrated significant antiviral activity in early clinical stages, its development faced hurdles in Phase 3 trials due to efficacy concerns in specific patient populations and the potential for resistance mutations like S324N (ClinicalTrials.gov NCT03376321). Despite these challenges, PB2 remains a high-interest target for broad-spectrum influenza therapies due to its conserved nature across various Influenza A strains.

Other names

Polymerase basic protein 2RNA-directed RNA polymerase subunit PB2PB2 proteinPBP2

Inhibition of the cap-binding domain of the PB2 subunit, which prevents the virus from capturing host pre-mRNA 5' caps required for priming viral mRNA synthesis.