TY - JOUR
T1 - Dephosphorylation of Sp1 at Ser-59 by Protein Phosphatase 2A (PP2A) is required for induction of CYP1A1 transcription after treatment with 2,3,7,8-tetrachlorodibenzo-p-dioxin or omeprazole
AU - Shimoyama, Shuji
AU - Kasai, Shuya
AU - Kahn-Perlès, Brigitte
AU - Kikuchi, Hideaki
N1 - Funding Information:
This work was supported in part by a Grant-in-aid for Science Research (C) (No. 21510065 ) from the Ministry of Education, Culture, Sports, Science and Technology (Monbu Kagakusho) , and the Global Environment Research Fund of the Ministry of the Environment, Japan ( C-0803 ).
PY - 2014/2
Y1 - 2014/2
N2 - The aryl hydrocarbon receptor (AhR) is a transcription factor that is activated by either 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) or omeprazole (OP). Activated AhR can induce CYP1A1 transcription by binding to the xenobiotic responsive element (XRE). However, the mechanism of activation of the CYP1A1 promoter region is poorly understood. Previous reports showed that Sp1 could bind to a GC-rich region near the CYP1A1 promoter. This study sought to clarify the function of Sp1 in CYP1A1 transcription. Phosphorylation of Sp1 at Ser-59 (pSer-59) was previously reported to be closely related to transcriptional regulation. We used a site-specific phospho-antibody to show that treatment with TCDD or OP drastically reduced the level of pSer-59 in Sp1 from HepG2 cells. This reduction was too much, we hypothesized that the reduced phosphorylation level resulted from activation of phosphatase activity. Given that pSer-59 is dephosphorylated by PP2A, we examined the effect of a PP2A inhibitor, okadaic acid (OA), on pSer-59 and transcription of CYP1A1. The results showed that OA blocked dephosphorylation of Ser-59 and drastically inhibited transcription of CYP1A1. Similar results were obtained after knockdown of PP2A. Treatment with OA had no effect on the expression of AhR, its nuclear translocation, or its ability to bind to the XRE. Furthermore, dephosphorylation of Sp1 at Ser-59 was not affected by knockdown of AhR. These results indicate that the signals from TCDD or OP caused PP2A-mediated dephosphorylation of Sp1 at Ser-59 and induced CYP1A1 transcription. This signaling pathway was independent of the AhR-mediated pathway.
AB - The aryl hydrocarbon receptor (AhR) is a transcription factor that is activated by either 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) or omeprazole (OP). Activated AhR can induce CYP1A1 transcription by binding to the xenobiotic responsive element (XRE). However, the mechanism of activation of the CYP1A1 promoter region is poorly understood. Previous reports showed that Sp1 could bind to a GC-rich region near the CYP1A1 promoter. This study sought to clarify the function of Sp1 in CYP1A1 transcription. Phosphorylation of Sp1 at Ser-59 (pSer-59) was previously reported to be closely related to transcriptional regulation. We used a site-specific phospho-antibody to show that treatment with TCDD or OP drastically reduced the level of pSer-59 in Sp1 from HepG2 cells. This reduction was too much, we hypothesized that the reduced phosphorylation level resulted from activation of phosphatase activity. Given that pSer-59 is dephosphorylated by PP2A, we examined the effect of a PP2A inhibitor, okadaic acid (OA), on pSer-59 and transcription of CYP1A1. The results showed that OA blocked dephosphorylation of Ser-59 and drastically inhibited transcription of CYP1A1. Similar results were obtained after knockdown of PP2A. Treatment with OA had no effect on the expression of AhR, its nuclear translocation, or its ability to bind to the XRE. Furthermore, dephosphorylation of Sp1 at Ser-59 was not affected by knockdown of AhR. These results indicate that the signals from TCDD or OP caused PP2A-mediated dephosphorylation of Sp1 at Ser-59 and induced CYP1A1 transcription. This signaling pathway was independent of the AhR-mediated pathway.
KW - Aryl hydrocarbon receptor
KW - CYP1A1
KW - Protein phophatase 2A
KW - Sp1
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U2 - 10.1016/j.bbagrm.2013.12.004
DO - 10.1016/j.bbagrm.2013.12.004
M3 - Article
C2 - 24382322
AN - SCOPUS:84892838225
VL - 1839
SP - 107
EP - 115
JO - Biochimica et Biophysica Acta - Gene Regulatory Mechanisms
JF - Biochimica et Biophysica Acta - Gene Regulatory Mechanisms
SN - 1874-9399
IS - 2
ER -