Short Article Opposed Regulation of Corepressor CtBP by SUMOylation and PDZ Binding

Summary binding proteinof adenovirus E1A)is a 48kDa corepres- sorandisoftenassociatedwithtranscriptionrepressors The transcription corepressor CtBP is often recruited via a PxDLS motif (Boyd et al., 1993; Schaeper et al.,tothetargetpromoterviainteractionwithaconserved 1995). CtBP represses transcription in both a HDAC- PxDLS motif in the interacting repressor. In this study, dependent or -independent manner, depending on thewe demonstrate that CtBP1 was SUMOylated and that promotercontext.Inhuman,twomembersofCtBPhave its SUMOylation profoundly affected its subcellular lo- been identified, CtBP1 (the original E1A-interactingcalization. SUMOylation occurred at a single Lys resi- CtBP) (Boyd et al., 1993; Schaeper et al., 1995) and due, Lys428, of CtBP1. CtBP2, a close homolog of CtBP2 (Katsanis and Fisher, 1998; Turner and Crossley,CtBP1,lackedtheSUMOylationsiteandwasnotmodi- 1998).ThetwoCtBPsmayhavedistinctrolesindevelop- fied by SUMO-1. Mutation of Lys428 into Arg (K428R) ment, considering their differential expression patternsshiftedCtBP1fromthenucleustothecytoplasm,while