Sumoylation of UL44 <i>in vitro</i>.

<p>(<b>A</b>) To analyze UL44 sumoylation <i>in vitro</i>, purified 6His-UL44 was incubated in the absence or the presence of sumoylation enzymes and either wild-type SUMO-1 (SUMO-1 wt) or a mutant form of SUMO-1 (SUMO-1 mut) which cannot be covalently linked to substrates. The reaction products were analyzed by western blotting with anti-UL44 and anti-SUMO-1 antibodies. As a positive control, <i>in vitro</i> sumoylation of p53 was also analyzed. (<b>B</b>) Purified 6His-UL44 was incubated in the absence or the presence of sumoylation enzymes and either SUMO-2 or SUMO-3 and analyzed by western blotting with anti-UL44 and anti-SUMO-2/−3 antibodies. For all panels, the arrowhead indicates the unmodified form of UL44 or p53 and the asterisks indicate the respective sumoylated forms.