The autophagy receptor SQSTM1/p62 is a restriction factor of HCMV infection

Background: Intrinsic defence mechanisms are pivotal host strategies to restrict viruses already at early stages of their infection. Here we addressed the question how the autophagy receptor sequestome 1 (SQSTM1/p62, herein termed p62) interfered with human cytomegalovirus (HCMV) infection. (2) Methods: CRISPR/Cas9- mediated genome editing, mass spectrometry and expression of p62 phosphovariants from recombinant HCMVs were used to address the role of p62 during infection. (3) Results: Knockout of p62 led to enhanced HCMV progeny release. Mass spectrometry revealed an interaction of p62 with cellular proteins required for nucleo-cytoplasmic transport. Phosphoproteomics further revealed that p62 is hyperphosphorylated at position S272 in HCMV-infected cells. Phosphorylated p62 showed enhanced nuclear retention, concordant with enhanced interaction with viral proteins relevant for genome replication and nuclear capsid egress. This modification led to reduced HCMV progeny release, compared to a unphosphorylated version of p62. (4) Conclusions: p62 is a restriction factor for HCMV replication The activity of the receptor appears to be regulated by phosphorylation at position S272, leading to enhanced nuclear localization, viral protein degradation and impairment of progeny production.