Sumoylation at the Host-Pathogen Interface

Wilson, Van G.

There are now well documented examples of pathogens that express proteins that mimic either SUMO proteases or SUMO ligases. Xanthomonas campestris, a plant pathogen, uses a type III secretion system to inject effector proteins into host cells during infection. Among the injected effectors are two proteins, XopD and AvrXv4, that both decrease overall host sumoylation [70] [71] [72] . XopD resembles the yeast SUMO protease, Ulp1, can deconjugate SUMO from substrates in vitro and in vivo, and causes an overall decrease in host sumoylation when exogenously expressed [70] . In a subsequent study it was confirmed that XopD is a virulence factor in tomatoes and that virulence at least partially requires the protease activity, though the critical target(s) for desumoylation were not identified [72] . A second Xanthomonas protein, AvrXv4, resembles a cysteine protease and causes desumoylation in plants [71] . However, in vitro SUMO protease activity by AvrXv4 could not be demonstrated raising the possibility that AvrXv4 is not directly a SUMO protease but somehow influences cellular SUMO proteases. Like XopD, AvrXv4 has a role in virulence, and the combined results strongly suggest that Xanthomonas is using SUMO deconjugation to alter the host cell environment to favor bacterial infection.