Viruses and sumoylation: recent highlights

Abstract

Since its discovery in 1997, SUMO (small ubiquitin-like modifier) has been implicated in a range of activities, indicating that this protein is as important in the cell as ubiquitin is. Although it can function throughout the cell, it appears to be involved more in nuclear functions. The growing list of substrates that are covalently modified by SUMO includes many viral proteins; SUMO appears to facilitate viral infection of cells, making it a possible target for antiviral therapies. It therefore is important to understand how viruses manipulate the cellular sumoylation system and how sumoylation affects viral functions.

Figure 1

The viral proteins discussed in this review and their interaction with the SUMO pathway. The upper panel shows how viral proteins could counteract the host's sumoylation, either by preventing de novo sumoylation (HCMV-IE1), by enhancing de-sumoylation (HSV-ICP0) or by inhibiting the sumoylation enzymatic cascade (Gam1; middle panel). Some viral proteins could exploit the host's sumoylation because they need to be SUMO-modified in order to exert their functions (lower panel). Abbreviations: S, SUMO; E1, SUMO-activating enzyme (SAE1/SAE2); E2, SUMO-conjugating enzyme (UBC9); E3, SUMO-ligases.