PSGL-1 is an evolutionarily conserved antiviral restriction factor

The arms race between viruses and their hosts shaped the evolutionary history and the genome composition of both parties. Restriction factors are the first-line antiviral effectors encoded by the host genomes and are often conserved through evolution to protect the hosts from morbidity, mortality, and even extinction associated with viral infections. There are a number of restriction factors identified so far to counteract HIV infection of the humans. PSGL-1 is a recently characterized human restriction factor that acts both early and late in the viral life cycle, the latter of which is antagonized by the HIV-1 Vpu protein. Here we show in vitro and in a knockout mouse model that PSGL-1's antiviral function is conserved in mice for combating the murine leukemia virus (MLV). In counter-strike, the glycogag or glycoMA proteins encoded by MLV can interact with mouse PSGL-1, which leads to Cul3-KLHL20 E3 ligase-dependent ubiquitination and degradation of PSGL-1. The amino acids involved in this interaction demonstrate the evidence of positive selection, manifesting the evolution pressure from the antagonism between PSGL-1 and glycogag/glycoMA. Our data support that PSGL-1 is an evolutionarily conserved antiviral restriction factor.