Mitogen- and Stress-Activated Protein Kinase 1 Mediates Alcohol-Upregulated Transcription of Brf1 and tRNA Genes to Cause Phenotypic Alteration

Abstract

Upregulation of Brf1 (TFIIB-related factor 1) and Pol III gene (RNA polymerase III-dependent gene, such as tRNAs and 5S rRNA) activities is associated with cell transformation and tumor development. Alcohol intake causes liver injury, such as steatosis, inflammation, fibrosis, and cirrhosis, which enhances the risk of HCC development. However, the mechanism of alcohol-promoted HCC remains to be explored. We have designed the complementary research system, which is composed of cell lines, an animal model, human samples, and experiments in vivo and in vitro, to carry out this project by using molecular biological, biochemical, and cellular biological approaches. It is a unique system to explore the mechanism of alcohol-associated HCC. Our results indicate that alcohol upregulates Brf1 and Pol III gene (tRNAs and 5S rRNA) transcription in primary mouse hepatocytes, immortalized mouse hepatocyte-AML-12 cells, and engineered human HepG2-ADH cells. Alcohol activates MSK1 to upregulate expression of Brf1 and Pol III genes, while inhibiting MSK1 reduces transcription of Brf1 and Pol III genes in alcohol-treated cells. The inhibitor of MSK1, SB-747651A, decreases the rates of cell proliferation and colony formation. Alcohol feeding promotes liver tumor development of the mouse. These results, for the first time, show the identification of the alcohol-response promoter fragment of the Pol III gene key transcription factor, Brf1. Our studies demonstrate that Brf1 expression is elevated in HCC tumor tissues of mice and humans. Alcohol increases cellular levels of Brf1, resulting in enhancement of Pol III gene transcription in hepatocytes through MSK1. Our mechanism analysis has demonstrated that alcohol-caused high-response fragment of the Brf1 promoter is at p-382/+109bp. The MSK1 inhibitor SB-747651A is an effective reagent to repress alcohol-induced cell proliferation and colony formation, which is a potential pharmaceutical agent. Developing this inhibitor as a therapeutic approach will benefit alcohol-associated HCC patients.

[Retracted] ROS Signaling‐Mediated Novel Biological Targets: Brf1 and RNA Pol III Genes

“…Emerging studies have clearly demonstrated that alcohol consumption is an established risk factor for breast cancer [ 22 – 25 ]. Approximately 80% of all cases of breast cancer are ER+ (estrogen receptor-positive) and 20% ER- (estrogen receptor-negative) [ 1 , 2 , 10 ]. Alcohol intake is associated with ER+ cases of breast cancer more than ER- cases [ 1 ].…”

“…Deregulation of Brf1 and Pol III genes is tightly linked to cell proliferation, cell transformation, and tumor development [ 4 – 9 ]. Brf1 is overexpressed in several human cancers, such as hepatocellular carcinoma, breast cancer, gastric cancer, prostate cancer, and lung cancer [ 5 , 8 , 10 – 13 ], while carcinogens, such as EGF (epidermal growth factor), DEN (Diethylnitrosamine), and MNNG (N-methyl-N′-nitro-N-nitrosoguanidine), and dietary factors (alcohol) induce the deregulation of Brf1 and Pol III genes [ 4 , 7 , 10 , 13 , 14 ]. This shows that the deregulation of Brf1 and Pol III genes plays a critical role in tumor development.…”

“…The deregulation of Brf1 and Pol III genes is mediated by different signaling pathways. Our studies and others have indicated that MAPK (mitogen-activated protein kinase) subfamily members (ERKs, p38 kinases, and JNKs), MSK1 (mitogen- and stress-activated protein kinase 1), PLK1 (polo-like kinase 1, also called serine/threonine-protein kinases), and AMPK (5′ AMP-activated protein kinase or 5′ adenosine monophosphate-activated protein kinase) pathways involve the modulation of the activities of Brf1 and Pol III genes [ 4 – 7 , 10 , 11 ]. Therefore, investigating the signaling pathways which mediate the deregulation of these genes and identifying specific inhibitors may provide potential approaches for the treatments of human cancers.…”

Exploring the Role and Mechanism of pAMPKα‐Mediated Dysregulation of Brf1 and RNA Pol III Genes

“…E1910). The luciferase activities of the lysates were normalized to their protein amounts as described [ 31 , 32 ]. The changes in luciferase activity were compared to the luciferase activity in the absence of MNNG.…”

“…Our earlier studies have demonstrated that alcohol increases Brf1 expression in tissue culture and animal models, which facilitates cell proliferation and transformation, and tumor formation [15,17,19,20,[29][30][31][32]. Chronic alcohol consumption results in the production of acetaldehyde and CYP2E1 induction (Cytochrome P450 2E1) [14].…”