Herpesvirus DNA polymerase processivity factors: Not just for DNA synthesis

•All mammalian herpesviruses encode a DNA polymerase processivity factor.•Conservation of structure with cellular sliding clamps.•DNA binding capabilities.•Multiple roles in DNA replication.•Additional diverse functions in transcription and cellular manipulation. Herpesviruses encode multiple proteins directly involved in DNA replication, including a DNA polymerase and a DNA polymerase processivity factor. As the name implies, these processivity factors are essential for efficient DNA synthesis, however they also make additional contributions to DNA replication, as well as having novel roles in transcription and modulation of host processes. Here we review the mechanisms by which DNA polymerase processivity factors from all three families of mammalian herpesviruses contribute to viral DNA replication as well as to additional aspects of viral infection.