title: Transcriptionally mediated inhibition of telomerase of fungal immunomodulatory protein from Ganoderma tsugae in A549 human lung adenocarcinoma cell line.
abstract: Telomerase expression is the hallmark of tumor cells, and activation of this ribonucleoprotein complex may be a rate-limiting or critical step in cellular immortalization and oncogenesis. Fungal immunomodulatory protein, FIP-gts, has been isolated from Ganoderma tsugae. In the present study, we expressed and purified the recombinant fungal immunomodulatory protein reFIP-gts in E. coli. We found that reFIP-gts significantly and selectively inhibits the growth of A549 cancer cells while not affecting the growth of normal MRC-5 fibroblasts. The reFIP-gts suppression of telomerase activity is concentration-dependent, due to the downregulation of the telomerase catalytic subunit (hTERT). It also happens at the mRNA level. These results were confirmed by transient transfections of A549 cells with pGL3-Basic plasmid constructs containing the functional hTERT promoter and its E-box-deleted sequences cloned upstream of a luciferase reporter gene. With electrophoretic mobility shift assays and Western blotting, we demonstrated that in response to reFIP-gts, binding of c-myc transcriptional factor to the E-box sequence on the hTERT promoter is inhibited. These results show that reFIP-gts suppresses telomerase activity and inhibits transcriptional regulation of hTERT via a c-myc-responsive element-dependent mechanism. Our findings provide new insight into both the anticancer function of reFIP-gts and the regulation of hTERT/telomerase expression, which may be valuable in the development of a promising chemopreventive agent.
authors.affiliation: Institute of Medical and Molecular Toxicology, Chung Shan Medical University, Taichung, Taiwan, Republic of China.
authors.forename: Chien-Huang
authors.initials: CH
authors.lastname: Liao
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Hsiao
authors.forename: Chung-Ping
authors.initials: CP
authors.lastname: Hsu
authors.forename: Meei-Yn
authors.initials: MY
authors.lastname: Lin
authors.forename: James Chun-Huan
authors.initials: JC
authors.lastname: Wang
authors.forename: Yu-Lu
authors.initials: YL
authors.lastname: Huang
authors.forename: Jiunn-Liang
authors.initials: JL
authors.lastname: Ko
mesh_terms: D000230:Adenocarcinoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D024721:E-Box Elements / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D005347:Fibroblasts; D005656:Fungal Proteins / Q000235:genetics / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D037102:Lectins / Q000235:genetics / Q000494:pharmacology*; D008156:Luciferases / Q000378:metabolism; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D037102:Lectins; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; D008156:Luciferases; D019098:Telomerase