Regulation of mammalian ribonucleotide reductase by the tumor promoters and protein phosphatase inhibitors okadaic acid and calyculin A

A rapid elevation of ribonucleotide reductase activity was observed with BALB c/3T3 fibroblasts treated with 10 nM okadaic acid, a nonphorbol ester tumor promoter and protein phosphatase inhibitor. Northern blot analysis of the two components of ribonucleotide reductase (R1 and R2) showed a marked elevation of R1 and R2 mRNA expression. Western blot analysis with R1 and R2 specific monoclonal antibodies indicated that the increase in ribonucleotide reductase activity was primarily due to the elevation of the R2 rather than the R1 protein during treatment with okadaic acid. The okadaic acid induced elevations in R1 and R2 message levels occurred without a detectable change in the proportion of cells in S phase and were blocked by treatment of cells with actinomycin D, indicating the importance of the reductase transcriptional process in responding to the action of okadaic acid. Furthermore, down-regulation of protein kinase C with 12-O-tetradecanoylphorbol-13-acetate pretreatment abrogated the okadaic acid mediated elevation of ribonucleotide reductase mRNAs, consistent with the involvement of this signal pathway in the regulation of ribonucleotide reductase and the effects of okadaic acid. Treatment of cells with 2.5 nM calyculin A, another non-phorbol ester tumor promoter and protein phosphatase inhibitor, resulted in a rapid elevation of both R1 and R2 mRNA levels within 10 min of treatment. This first demonstration that the non-phorbol ester tumor promoters and protein phosphatase inhibitors can cause rapid alterations in ribonucleotide reductase gene expression suggests that (i) ribonucleotide reductase, particularly the R2 component, plays a fundamental role in the critical early events involved in the process of tumor promotion, and (ii) illustrates a role for cellular protein phosphatases in the regulation of ribonucleotide reductase and, through this process, the regulation of DNA synthesis.PT: J; CR: ANGEL P, 1987, CELL, V49, P729 BIOLOJAN C, 1988, BIOCHEM J, V256, P283 CHOY BK, 1988, CANCER RES, V48, P2929 CHOY BK, 1989, BIOCHEM BIOPH RES CO, V162, P1417 COHEN P, 1990, TRENDS BIOCHEM SCI, V15, P98 EDWARDS DR, 1985, MOL CELL BIOL, V5, P3280 ERDODI F, 1988, BIOCHEM BIOPH RES CO, V153, P156 ERIKSSON S, 1984, J BIOL CHEM, V259, P11695 GOUGH NM, 1988, ANAL BIOCHEM, V173, P93 HARDS RG, 1981, J CELL PHYSIOL, V106, P309 HAYSTEAD TAJ, 1972, NATURE, V247, P3336 HOPPER S, 1972, J BIOL CHEM, V247, P3336 HURTA RAR, 1990, BIOCHEM BIOPH RES CO, V167, P258 HURTA RAR, 1990, BIOCHIM BIOPHYS ACTA, V1087, P165 HURTA RAR, 1991, J BIOL CHEM, V266, P24097 HURTA RAR, 1992, J BIOL CHEM, V267, P7066 LEWIS WH, 1978, J CELL PHYSL, V94, P287 MANN GJ, 1988, CANCER RES, V48, P5151 MCCLARTY GA, 1987, BIOCHEMISTRY-US, V26, P8004 MCCLARTY GA, 1990, J BIOL CHEM, V265, P7539 NISHIZUKA Y, 1986, SCIENCE, V233, P305 PERTOVAARA L, 1989, MOL CELL BIOL, V9, P1255 PHILLIPS DR, 1986, BIOCHEMISTRY-US, V25, P7355 SASSA T, 1989, BIOCHEM BIOPH RES CO, V159, P939 STEEPER JR, 1970, ANAL BIOCHEM, V34, P123 SUGANUMA M, 1988, P NATL ACAD SCI USA, V85, P1768 SUGANUMA M, 1990, CANCER RES, V50, P3521 THELANDER M, 1985, J BIOL CHEM, V260, P2737 THEVENIN C, 1991, J BIOL CHEM, V266, P9363 WRIGHT JA, 1987, SOMAT CELL MOLEC GEN, V13, P155 WRIGHT JA, 1989, INT ENCY PHARM THERA, V128, P89 WRIGHT JA, 1990, BIOCH CELL BIOL, V68, P1364 YOUNG S, 1987, BIOCHEM J, V244, P775; NR: 33; TC: 18; J9: BIOCHEM CELL BIOL; PG: 7; GA: KQ352Source type: Electronic(1