Negative Regulation of NF-κB Signaling by PIAS1

Abstract

The NF-B family of transcription factors is activated by a wide variety of signals to regulate a spectrum of cellular processes. The proper regulation of NF-B activity is critical, since abnormal NF-B signaling is associated with a number of human illnesses, such as chronic inflammatory diseases and cancer. We report here that PIAS1 ( and bacterial lipopolysaccharide (LPS), activate the NF-B signaling pathway. NF-B is a family of dimeric transcription factors composed of members of the Rel family of DNA binding proteins, including NF-B1 (p50 and its precursor p105), NF-B2 (p52 and its precursor p100), c-Rel, RelA (p65), and RelB (11, 18). Upon stimulation, NF-B translocates into the nucleus, where it binds to specific DNA sequences and regulates transcription. NF-B is involved in mediating a wide spectrum of cellular responses, including infections, inflammation, and apoptosis (2, 27). Inappropriate regulation of NF-B is involved in a wide range of human diseases, including cancer, neurodegenerative disorders, arthritis, asthma, and chronic inflammation (3,4,10,12). The NF-B signaling pathway is tightly modulated at various levels by distinct regulatory proteins. For example, the binding of the IB family of proteins prevents the nuclear translocation of NF-B (16). However, a protein factor that can regulate the DNA binding activity of NF-B has not been documented.The PIAS (protein inhibitor of activated STAT) family of proteins consists of four members: PIAS1, PIAS3, PIASx, and PIASy (33). Members of the PIAS family have been suggested to regulate STAT-mediated transcription. Upon cytokine stimulation, PIAS binds to STAT and inhibits STAT-mediated gene activation (1,8,21,22). Among the PIAS family, PIAS1 and PIASy have been shown to inhibit STAT1-dependent transcription through distinct mechanisms. PIAS1 inhibits the transcriptional activity of STAT1 by blocking the DNA binding activity of STAT1. In contrast, PIASy does not affect the DNA binding activity of STAT1. It has been suggested that PIASy may act as a transcriptional corepressor of STAT1. The PIAS family of proteins has also been suggested to regulate a number of other transcription factors, including nuclear hormone receptors (13,28,36,37), LEF1 (31), and p53 (15,26,32).To understand the physiological role of PIAS1, we have recently generated Pias1 null mice (23). Detailed gene activation analysis indicates that PIAS1 selectively regulates a subset of interferon (IFN)-inducible genes. The antiviral activity of IFNs is significantly enhanced by Pias1 disruption. In addition, Pias1 null mice show enhanced protection against pathogenic infection. These results support a physiological role of PIAS1 in the negative regulation of IFN-activated STAT1-mediated gene activation and demonstrate an important role of PIAS1 in innate immune responses.Since STAT1 and the Rel family of proteins share structural similarity in their DNA binding domains (6), we explored the possible involvement of PIAS1 in the regulation of NF-B. Here we report that PIAS1 interacts with ...

Regulation of cytokine signaling pathways by PIAS proteins

“…In addition, PIAS1 repressed the transcriptional activity of a GAL4-p65 fusion protein when assayed using the κB reporter, but not the GAL4 reporter. Consistently, ChIP assays showed that the recruitment of p65 to the endogenous promoter of IκBα, a known NF-κB-target gene, was inhibited in PIAS1-overexpressing cells, but was enhanced in PIAS1-deficient cells [31].…”

“…In NF-κB reporter assays, PIAS1 and PIAS3 can repress the transcriptional activity of p65 [31,40]. In addition, the induction of several endogenous NF-κB-target genes, such as those encoding IκBα and Bfl-1, in response to TNF stimulation was inhibited in PIAS1-overexpression cells [31]. Similar to the case of STAT1, purified PIAS1 inhibited the DNA binding activity of NF-κB in mobility gel-shift assays.…”

“…The transcription of IκBa, IL-1β and JunB in response to TNF-α treatment was enhanced in Pias1 null cells as compared to that in wild type controls, while the induction of other NF-κB target genes, including Cxcl10 (CXC-chemokine ligand 10), Nos2, and Mcp1 (Monocyte chemotactic protein-1), was not significantly affected in the absence of PIAS1 [31]. Detailed microarray studies showed that PIAS1 affects approximately 48% of TNF-induced genes.…”

“…Both PIAS1 and PIAS3 can interact with NF-κB p65 [31,40]. In NF-κB reporter assays, PIAS1 and PIAS3 can repress the transcriptional activity of p65 [31,40]. In addition, the induction of several endogenous NF-κB-target genes, such as those encoding IκBα and Bfl-1, in response to TNF stimulation was inhibited in PIAS1-overexpression cells [31].…”

“…Both PIAS1 and PIAS3 can interact with NF-κB p65 [31,40]. In NF-κB reporter assays, PIAS1 and PIAS3 can repress the transcriptional activity of p65 [31,40].…”