title: Suppression of STAT3 activity by Duplin, which is a negative regulator of the Wnt signal.
abstract: Duplin was originally isolated as a negative regulator of beta-catenin-dependent T-cell factor (Tcf) transcriptional activity in the Wnt signaling pathway. However, Duplin knockout mice exhibit embryonic lethality at 5.5-em day, suggesting that Duplin has important roles other than as a negative regulator of the Wnt signal. To identify new roles of Duplin, the Duplin-binding proteins were screened. PIAS3, which is a SUMO E3 ligase and acts as an inhibitor of signal transducer and activator of transcription (STAT3), was identified as a Duplin-binding protein. Duplin was sumoylated, but PIAS3 affected neither the sumoylation of Duplin nor its ability to inhibit Tcf-4 activity. Like PIAS3, Duplin suppressed the leukemia-inhibitory factor (LIF)-induced STAT3 transcriptional activity. Duplin did not affect the LIF-dependent tyrosine phosphorylation or nuclear localization of STAT3 but inhibited the formation of complex between STAT3 and DNA. Although STAT3 is not modified with SUMO, PIAS3 inhibited the STAT3 activity in a manner partially depending on its SUMO E3 ligase activity. Duplin suppressed the LIF-dependent STAT3 activity independently of sumoylation. These results demonstrate that Duplin inhibits not only Tcf-4 but also STAT3, suggesting that Duplin may act as a repressor for multiple transcriptional factors.
authors.affiliation: Department of Biochemistry, Graduate School of Biomedical Sciences, Hiroshima University, 1-2-3 Kasumi, Hiroshima 734-8551, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Yamashina
authors.forename: Hideki
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Chayama
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakajima
authors.forename: Akira
authors.initials: A
authors.lastname: Kikuchi
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D004247:DNA / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000494:pharmacology / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D011485:Protein Binding; D050828:Protein Inhibitors of Activated STAT / Q000737:chemistry / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051153:Wnt Proteins / Q000187:drug effects / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D050828:Protein Inhibitors of Activated STAT; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D051153:Wnt Proteins; C515814:duplin protein, mouse; D004247:DNA