For the virus life cycle, it could be a mechanism to favour early viral gene expression because: (i) similar to murine polyomavirus, AP-1 expression was upregulated upon JCPyV infection [113], (ii) AP-1 stimulates transcription from the JCPyV early promoter [114], and (iii) LT usurps AP-1, which prevents viral replication and late gene expression [112]. Here, JUNB is linked to infection.