Sumoylation of Daxx Regulates IFN-Induced Growth Suppression of B Lymphocytes and the Hormone Receptor-Mediated Transactivation

Abstract

Daxx has been shown to play an essential role in type I IFN-mediated suppression of B cell development and apoptosis. Recently, we demonstrated that Tyk2 is directly involved in IFN signaling for the induction and translocation of Daxx, which may result in growth arrest and/or apoptosis of B lymphocyte progenitors. To clarify the molecular mechanisms of how Daxx acts on growth suppression of B lymphocytes, we examined functions of a sumoylation-defective Daxx KA mutant (Daxx K630/631A), which substituted Lys 630 and Lys 631 to Ala. Importantly, Daxx KA localized in the cytoplasm, whereas wild-type Daxx localized in the nucleus. Murine pro-B cell line Ba/F3 expressing Daxx KA revealed a resistance to the IFN-induced growth suppression. It is noteworthy that treatment with an exportin inhibitor, leptomycin B, resulted in nuclear localization of Daxx KA and recovery of the IFN-induced growth suppression in Ba/F3 cells. Moreover, Daxx KA decreased the binding potential to promyelocytic leukemia protein (PML), and overexpression of PML recruited Daxx KA into PML oncogenic domains. Notably, a Daxx-small ubiquitin-related modifier fusion protein exhibited increased nuclear localization and ability to suppress cell growth in Ba/F3 cells. These results demonstrate that the IFN-induced growth suppression of B lymphocytes requires nuclear localization of Daxx through its sumoylation and proper interactions with PML.

Sumoylation of Smad3 stimulates its nuclear export during PIASy-mediated suppression of TGF-β signaling

“…Yellow-emitting (YFP)-SUMO1, cyan-emitting (CFP)-Smad3 and SUMO1-Smad3 constructs were generated by PCR methods and sequenced as described previously [11,12]. Anti-HA, anti-Smad3, and anti-phospho-Smad3 (Ser 433/435) antibodies were purchased from Santa Cruz Biotechnology (Santa Cruz, CA).…”

“…It has been recently shown that SUMO-fusion proteins behave similarly to that of physiologically sumoylated proteins [12,24]. Expression vectors for FLAG-tagged Smad3 or SUMO1-Smad3 were transfected into Hep3Bcells and treated with or without TGF-b.…”

Interferon controls SUMO availability via the Lin28 and let-7 axis to impede virus replication

“…40). Often in their sumoylated forms, some partners have been implicated in IFN effects on senescence (DAXX, p53, SP100) or antiviral defence (SP100) [41][42][43][44][45][46] . These unexpected findings therefore point to the existence of a highly integrated regulatory loop wherein the substrates, their modifiers (SUMOs) and the catalyser (PML NBs) are all dramatically upregulated during IFN response, promoting the rapid formation of the active, SUMO-conjugated form.…”

Kaposi's sarcoma-associated herpesvirus-encoded LANA associates with glucocorticoid receptor and enhances its transcriptional activities

“…RU486 was purchased from Sigma-Aldrich (St Louis, MO, USA). Expression vectors, MMTV-LUC, GRE-LUC, GR, epitope-tagged GR, LANA and LANA deletion mutants were described previously [13,30,31]. Anti-Myc, -GR and -Tublin antibodies were purchased from Santa Cruz Biotechnology (Santa Cruz, CA).…”

“…The cells were then reacted with FITC-conjugated anti-rabbit IgG or rhodamine-conjugated anti-mouse IgG (Chemicon) and observed under a confocal laser fluorescent microscope [31]. Images were obtained by using a Zeiss LSM 510 laser scanning microscope with an Apochromat x63/1.4 oil immersion objective and x4 zoom.…”