**Haidong Gu \* and Behdokht Jan Fada**

Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA; ga2861@wayne.edu **\*** Correspondence: haidong.gu@wayne.edu; Tel.: +1-313-577-6402

Received: 7 May 2020; Accepted: 5 June 2020; Published: 8 June 2020

**Abstract:** Ubiquitination is a prominent posttranslational modification, in which the ubiquitin moiety is covalently attached to a target protein to influence protein stability, interaction partner and biological function. All seven lysine residues of ubiquitin, along with the N-terminal methionine, can each serve as a substrate for further ubiquitination, which e ffectuates a diverse combination of monoor poly-ubiquitinated proteins with linear or branched ubiquitin chains. The intricately composed ubiquitin codes are then recognized by a large variety of ubiquitin binding domain (UBD)-containing proteins to participate in the regulation of various pathways to modulate the cell behavior. Viruses, as obligate parasites, involve many aspects of the cell pathways to overcome host defenses and subjugate cellular machineries. In the virus-host interactions, both the virus and the host tap into the rich source of versatile ubiquitination code in order to compete, combat, and co-evolve. Here, we review the recent literature to discuss the role of ubiquitin system as the infection progresses in virus life cycle and the importance of ubiquitin specificity in the regulation of virus-host relation.

**Keywords:** ubiquitin code; virus infection; virus-host interaction
