Effect of the activated Raf protein kinase on the human multidrug resistance 1 (MDR1) gene promoter.
Revealing the regulatory mechanism of the multidrug resistance 1 (MDR1) gene is important to gain understanding of MDR in tumor cells. Using MDR1 deletion constructs and the 22W mutant of c-Raf in which the NH2-terminal half has been deleted, we examined the effect of the activated Raf on human MDR1 promoter activity in transient expression assay and stable transfectants of GHE-L cells. A DNA sequence exhibiting strong activation of MDR1 promoter by 22W was located between -197 and -136 containing the upstream heat shock element (HSE) motifs without other regulatory elements, whereas the MDR1 deletion construct containing downstream HSE motif showed a relatively weaker activation by 22W. We observed that the activated Raf significantly potentiated the induction of MDRCAT activity in GHE-L cells by sodium arsenite or heat shock, which stimulates heat shock factor (HSF) binding to HSE. In addition, protein kinase A inhibitor (H-87) blocked the activation of the MDR1 promoter by 22W in GHE-L cells in a dose-dependent manner. From these results, we propose the possibility that Raf- and protein kinase A-dependent pathways control the transcription of MDR1 gene via a mechanism involving the modulation of HSF activity.
Kim
S H
SH
Department of Biochemistry, College of Medicine, Pusan National University, South Korea.
Lee
S H
SH
Kwak
N H
NH
Kang
C D
CD
Chung
B S
BS
D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D018432:Drug Resistance, Multiple / Q000235:genetics*; D004789:Enzyme Activation; D004988:Ethers, Cyclic / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D008647:Mesocricetus; D019319:Okadaic Acid; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D014162:Transfection
D004988:Ethers, Cyclic; D006360:Heat-Shock Proteins; D011518:Proto-Oncogene Proteins; D019319:Okadaic Acid; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf