title: SOCS-3 inhibits E2F/DP-1 transcriptional activity and cell cycle progression via interaction with DP-1.
abstract: Recent studies using SOCS family knock-out mice have suggested that SOCS proteins have multiple biological functions in addition to their role as negative regulators of JAK-STAT signaling. To explore these other functions of this family of proteins, we used yeast two-hybrid screening to find proteins interacting with human SOCS-3. We identified the transcriptional factor DP-1 as a SOCS-3-interacting protein involved in regulation of the cell cycle. Immunoprecipitation-Western blot assay showed that this interaction between these endogenous proteins occurred in cells both in vitro and in vivo. SOCS-3 interacted with the C-terminal region of DP-1, and amino acids 156-172 of SOCS-3 were required for this interaction. Confocal microscopy revealed that SOCS-3 and DP-1 were primarily colocalized in the cytoplasm. SOCS-3 inhibited E2F/DP-1 transcriptional activity under the cyclin-E promoter and actually inhibited cell cycle progression and cell growth under E2F/DP-1 control. In contrast, DP-1 almost completely eliminated the inhibitory action of SOCS-3 on LIF-stimulated STAT-3 transcriptional activity in JAK-STAT signaling. Interestingly, the alternative regulatory action of SOCS-3 and DP-1 was dramatically eliminated by each siRNA. Taken together, these findings demonstrate that SOCS-3 acts as a negative regulator of the cell cycle progression under E2F/DP-1 control by interfering with heterodimer formation between DP-1 and E2F and also that DP-1 plays an important role in controlling JAK-STAT signaling.
authors.affiliation: Department of Applied Biological Sciences, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa-city, Kanagawa 252-8510, Japan.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Masuhiro
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kayama
authors.forename: Akie
authors.initials: A
authors.lastname: Fukushima
authors.forename: Koji
authors.initials: K
authors.lastname: Baba
authors.forename: Makio
authors.initials: M
authors.lastname: Soutsu
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Michio
authors.initials: M
authors.lastname: Gotoh
authors.forename: Noboru
authors.initials: N
authors.lastname: Yamaguchi
authors.forename: Shigemasa
authors.initials: S
authors.lastname: Hanazawa
mesh_terms: D002453:Cell Cycle; D002460:Cell Line; D050684:E2F Transcription Factors / Q000378:metabolism*; D006801:Humans; D011485:Protein Binding; D050791:STAT Transcription Factors / Q000378:metabolism; D015398:Signal Transduction; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism*; D050680:Transcription Factor DP1 / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics*
chemical_list: D050684:E2F Transcription Factors; C106644:SOCS3 protein, human; D050791:STAT Transcription Factors; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; C493735:TFDP1 protein, human; D050680:Transcription Factor DP1