The green tea component EGCG inhibits RNA polymerase III transcription

Abstract

RNA polymerase III (RNA pol III) transcribes many small structural RNA molecules involved in RNA processing and translation, and thus regulates the growth rate of a cell. Accurate initiation by RNA pol III requires the initiation factor TFIIIB. TFIIIB has been demonstrated to be regulated by tumor suppressors, including ARF, p53, RB, and the RB-related pocket proteins, and is a target of the oncogene c-myc and the mitogen-activated protein kinase ERK. EGCG has been demonstrated to inhibit the growth of a variety of cancer cells, induce apoptosis and regulate the expression of p53, myc, and ERK. Thus, we hypothesized that EGCG may regulate RNA pol III transcription in cells. Here, we report that EGCG (1) inhibits RNA pol III transcription from gene internal and gene external promoters (2) EGCG inhibits protein expression of the TFIIIB subunits Brf1 and Brf2, and (3) EGCG inhibits Brf2 promoter activity in cervical carcinoma cells. KeywordsRNA polymerase III; TFIIIB; Brf1; Brf2; EGCG Catechins are flavonoids found in many plant-derived food products including fruits, berries, chocolate, wine, and green tea (Camellia sinensis) [1]. (−)-Epigallocatechin gallate (EGCG) (Figure 1) constitutes the largest percentage of catechins found in green tea, accounting for 65% of the total catechin content [2]. Epidemiological and animal studies have demonstrated that EGCG provides protection against a variety of cancers including those of the skin, lung, prostate and breast [3][4][5][6]. EGCG also possess anti-proteolytic [7,8], anti-mutagenic [9,10], and anti-proliferative [5,[11][12][13] activity, thereby regulating the growth of a cell.RNA polymerase III (RNA pol III) is the largest of the eukaryotic DNA dependent RNA polymerases, with 17 subunits, and transcribes many of the genes involved in processing (U6 snRNA) and translation (tRNA), thereby dictating the growth rate of a cell [14]. RNA pol III activity has been shown to be deregulated in a variety of cancers, reviewed in [15-© 2010 Elsevier Inc. All rights reserved 3 Corresponding author: Laura Schramm, Department of Biological Sciences, St. John's University, 8000 Utopia Parkway, Queens, NY 11439; schrammL@stjohns.edu; Fax: 718-990-5958. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Deregulation of TFIIIB-mediated transcription could be an important step in tumor development. Hence, we speculate that TFIIIB-mediated transcription may be a novel target of regulation by chemopreventive agents. NIH Public AccessEGCG and RNA polymerase III have both been demonstrated to regulate cell growth and proliferation. We hypothesi...

Gender Specific Differences in RNA Polymerase III Transcription

“…Our data shows that EGCG significantly inhibited both tMet (p<0.01) and U6 snRNA (p<0.05) RNA pol III transcription in a female derived AC cancer cell line (Figure 1A). These data agree with our previously published report demonstrating that EGCG inhibited all classes of RNA pol III transcription tested in the HeLa cervical cancer line [16]. Interestingly, EGCG treatment of the male AC lung cancer cells, A549, showed significant stimulation of tMet (p<0.05) transcription whereas U6 snRNA transcription was unaffected (Figure 1B).…”

“…Further, RNA pol III transcription has been demonstrated to be regulated by the purified green tea polyphenol EGCG in the HeLa cervical cancer cell line [16]. …”

“…Also, host proteins such as MAF1 negatively regulate RNA pol III transcription in response to internal and external cell signals [13–15]. Further, RNA pol III transcription is down regulated by chemopreventive agents such as the polyphenol EGCG in cervical cancer cells [16]. However, regulation of RNA pol III transcription by EGCG has not been demonstrated in other tissue types, nor has general RNA pol III transcription been investigated for gender specific differences.…”

Inhibition of RNA Polymerase III Transcription by BRCA1

“…Transiently transfected cells were harvested 48 h posttransfection, and dual-luciferase assays (Promega, Madison, WI) were performed as previously described. 12,14 Experiments were performed in triplicate and repeated three independent times, and the data presented are representative. One-way analysis of variance (ANOVA) with Tukey post-test at 95% confidence interval was performed using Graphpad Prism 3.03 (Graphpad, San Diego, CA).…”

“…HCC1937 cells were transiently transfected with the indicated vectors and harvested 48 h posttransfection, and luciferase assay was performed as previously described. 12,14 One-way ANOVA with Tukey post-test at 95% confidence interval was performed using Graphpad Prism 3.03. *p b 0.05; **p b 0.01; ***p b 0.001.…”