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Rap1 reverses transcriptional repression of TGF-beta type II receptor by a mechanism involving AP-1 in the human pancreatic cancer cell line, UK Pan-1.
J Cell Physiol 2003; 194(1):88-99JC

Abstract

The TGF-beta signaling pathway has potent anti-mitogenic effects in epithelial cells and loss of negative growth regulation is often associated with increased tumorigenicity. The human pancreatic ductal adenocarcinoma cell line, UK Pan-1, which expresses DPC4, is not highly responsive to TGF-beta due to transcriptional repression of TGF-beta type II receptor (RII). Here, we show that UK Pan-1 cells transfected with a plasmid to overexpress rap1 protein (UK/rap1) causes an increase in RII transcription and restores sensitivity to TGF-beta growth inhibition. The overexpression of rap1 was associated with diminished ras signaling as measured by ras binding domain (RBD)-binding assays. Electrophoretic mobility shift assays (EMSA) analysis revealed increased binding of nuclear proteins to a previously identified positive regulatory element (PRE1) of the RII promoter in rap1 transfected cells. Competition with an oligo containing the AP-1 consensus site was able to inhibit this binding of nuclear proteins to the PRE1 region. Further EMSA analysis using antibodies to various AP-1 components revealed that junB antibodies partially depleted the increase in binding to the PRE1 seen in UK/rap1 cells while antibodies to other AP-1 constituents such as c-jun, c-fos, and ATF-1 had no effect on binding. Consistent with this data, transient transfection of UK Pan-1 cells with junB resulted in greater RII transcription (twofold) as measured by RII-luciferase assay. Mutation of the AP-1 site inhibited junB-mediated or rap1-mediated increases in RII promoter activity. These data suggest that rap1 signaling may mediate an increase in RII transcription via increased binding of nuclear factors including junB to the PRE1 region of the RII promoter.

Authors+Show Affiliations

Department of Pharmacology, University of Texas Health Science Center, San Antonio 78229, USA.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

12447993

Citation

Fralix, Kimberly D., et al. "Rap1 Reverses Transcriptional Repression of TGF-beta Type II Receptor By a Mechanism Involving AP-1 in the Human Pancreatic Cancer Cell Line, UK Pan-1." Journal of Cellular Physiology, vol. 194, no. 1, 2003, pp. 88-99.
Fralix KD, Zhao S, Venkatasubbarao K, et al. Rap1 reverses transcriptional repression of TGF-beta type II receptor by a mechanism involving AP-1 in the human pancreatic cancer cell line, UK Pan-1. J Cell Physiol. 2003;194(1):88-99.
Fralix, K. D., Zhao, S., Venkatasubbarao, K., & Freeman, J. W. (2003). Rap1 reverses transcriptional repression of TGF-beta type II receptor by a mechanism involving AP-1 in the human pancreatic cancer cell line, UK Pan-1. Journal of Cellular Physiology, 194(1), pp. 88-99.
Fralix KD, et al. Rap1 Reverses Transcriptional Repression of TGF-beta Type II Receptor By a Mechanism Involving AP-1 in the Human Pancreatic Cancer Cell Line, UK Pan-1. J Cell Physiol. 2003;194(1):88-99. PubMed PMID: 12447993.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Rap1 reverses transcriptional repression of TGF-beta type II receptor by a mechanism involving AP-1 in the human pancreatic cancer cell line, UK Pan-1. AU - Fralix,Kimberly D, AU - Zhao,Shujie, AU - Venkatasubbarao,Kolaparthi, AU - Freeman,James W, PY - 2002/11/26/pubmed PY - 2003/1/9/medline PY - 2002/11/26/entrez SP - 88 EP - 99 JF - Journal of cellular physiology JO - J. Cell. Physiol. VL - 194 IS - 1 N2 - The TGF-beta signaling pathway has potent anti-mitogenic effects in epithelial cells and loss of negative growth regulation is often associated with increased tumorigenicity. The human pancreatic ductal adenocarcinoma cell line, UK Pan-1, which expresses DPC4, is not highly responsive to TGF-beta due to transcriptional repression of TGF-beta type II receptor (RII). Here, we show that UK Pan-1 cells transfected with a plasmid to overexpress rap1 protein (UK/rap1) causes an increase in RII transcription and restores sensitivity to TGF-beta growth inhibition. The overexpression of rap1 was associated with diminished ras signaling as measured by ras binding domain (RBD)-binding assays. Electrophoretic mobility shift assays (EMSA) analysis revealed increased binding of nuclear proteins to a previously identified positive regulatory element (PRE1) of the RII promoter in rap1 transfected cells. Competition with an oligo containing the AP-1 consensus site was able to inhibit this binding of nuclear proteins to the PRE1 region. Further EMSA analysis using antibodies to various AP-1 components revealed that junB antibodies partially depleted the increase in binding to the PRE1 seen in UK/rap1 cells while antibodies to other AP-1 constituents such as c-jun, c-fos, and ATF-1 had no effect on binding. Consistent with this data, transient transfection of UK Pan-1 cells with junB resulted in greater RII transcription (twofold) as measured by RII-luciferase assay. Mutation of the AP-1 site inhibited junB-mediated or rap1-mediated increases in RII promoter activity. These data suggest that rap1 signaling may mediate an increase in RII transcription via increased binding of nuclear factors including junB to the PRE1 region of the RII promoter. SN - 0021-9541 UR - https://www.unboundmedicine.com/medline/citation/12447993/Rap1_reverses_transcriptional_repression_of_TGF_beta_type_II_receptor_by_a_mechanism_involving_AP_1_in_the_human_pancreatic_cancer_cell_line_UK_Pan_1_ L2 - https://doi.org/10.1002/jcp.10192 DB - PRIME DP - Unbound Medicine ER -