Influenza A virus nucleoprotein is acetylated by histone acetyltransferases PCAF and GCN5

Abstract

Histone acetylation plays crucial roles in transcriptional regulation and chromatin organization. Viral RNA of the influenza virus interacts with its nucleoprotein (NP), whose function corresponds to that of eukaryotic histones. NP regulates viral replication and has been shown to undergo acetylation by the cAMP-response element (CRE)–binding protein (CBP) from the host. However, whether NP is the target of other host acetyltransferases is unknown. Here, we show that influenza virus NP undergoes acetylation by the two host acetyltransferases GCN5 and P300/CBP-associated factor (PCAF) and that this modification affects viral polymerase activities. Western blot analysis with anti–acetyl-lysine antibody on cultured A549 human lung adenocarcinoma epithelial cells infected with different influenza virus strains indicated acetylation of the viral NP. A series of biochemical analyses disclosed that the host lysine acetyltransferases GCN5 and PCAF acetylate NP in vitro. MS experiments identified three lysine residues as acetylation targets in the host cells and suggested that Lys-31 and Lys-90 are acetylated by PCAF and GCN5, respectively. RNAi-mediated silencing of GCN5 and PCAF did not change acetylation levels of NP. However, interestingly, viral polymerase activities were increased by the PCAF silencing and were decreased by the GCN5 silencing, suggesting that acetylation of the Lys-31 and Lys-90 residues has opposing effects on viral replication. Our findings suggest that epigenetic control of NP via acetylation by host acetyltransferases contributes to regulation of polymerase activity in the influenza A virus.

Role of Post-translational Modifications in Influenza A Virus Life Cycle and Host Innate Immune Response

“…The acetylation and phosphorylation of NP are actively involved in regulating influenza viral transcription. The host acetyltransferase GCN5 can acetylate NP K90, leading to increased IAV polymerase activities, whereas acetylation of NP K31 mediated by PCAF decreases polymerase activities (Hatakeyama et al, 2018) ( Table 1). The phosphorylation of NP can stimulate viral transcription, and NP must undergo specific conformational changes to ensure efficient transcriptional activity (Kamata and Watanabe, 1977).…”

Chemical and Biological Aspects of Garcinol and Isogarcinol: Recent Developments

“…Interestingly, both HATs target different lysines of the nucleoprotein: while PCAF acetylate Lys‐31, GCN5 acetylates Lys 90. Both lysines regulate opposite effects: deacetylated Lys‐31 (by suppression of PCAF) enhanced viral polymerase activities while deacetylated Lys‐90 (by suppression of GCN5) decreased the viral polymerase function …”

“…Both lysines regulate opposite effects: deacetylated Lys-31 (by suppression of PCAF) enhanced viral polymerase activities while deacetylated Lys-90 (by suppression of GCN5) decreased the viral polymerase function. [61] The lethal toxin (LT) of the Gram-positive bacterium Bacillus anthracis induces actin stress fiber formation in infected cells by suppression of HDAC expression and, thus, this process is controlled by histone acetylation. In contrast to LT, the HAT inhibitor garcinol reduced stress fiber formation in LT-treated HUVEC cells and so might act as an antidote for LT intoxication.…”

Flu’s cues: Exploiting host post-translational modifications to direct the influenza virus replication cycle

“…PB1, PA, and NP undergo N-terminal acetylation with no specific assigned functions [ 14 ]. NP is also acetylated on internal lysine residues [ 15 , 16 ]. Mimicking NP acetylation disrupts the ability of NP to stabilize replication intermediates.…”

“…Moreover, since certain amino acid residues can be subject to many different PTMs, a single residue may be competitively or differentially modified over time. Several examples of PTM cross-talk on influenza virus proteins have already been identified [ 8 , 12 , 16 ], suggesting additional levels of regulatory complexity. Additionally, continuing advances in detection and characterization of PTMs will undoubtedly uncover new facets of influenza virus biology [ 40 ].…”