Nucleic Acids Research, 2002, Vol. 30, No. 14 3286-3293
© 2002 Oxford University Press
Regulation of ribonuclease expression by estradiol in Rana catesbeiana (Bullfrog)
Institute of Biomedical Sciences, Academia Sinica, 128, Yen-Chiu-Yuan Road, Sec. 2, Taipei 115, Taiwan and 1 Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei 100, Taiwan
*To whom correspondence should be addressed. Tel: +886 2 2789 9167; Fax: +886 2 2782 9142; Email: ydliao{at}ibms.sinica.edu.tw
The authors wish it to be known that, in their opinion, the first two authors should be regarded as joint First Authors
+AF039104, AF288642.2
Multiple ribonucleases are widely found in living organisms, but the function and regulation of individual ribonucleases are still not clear. In the present study, we found that one oocytic ribonuclease, RC-RNase, is developmentally expressed in the liver and stored in the oocyte of the bullfrog, while another ribonuclease, RC-RNase L1, is constitutively expressed and retained in the liver at all stages. In females, the expression of RC-RNase increased with the degree of maturity and the concentration of plasma estradiol during oogenesis. In males, the RC-RNase gene was activated in the liver and the newly synthesized protein was secreted into plasma if estradiol was administered. To investigate the mechanism of estrogen-mediated activation of ribonuclease expression, we cloned the RC-RNase promoter and analyzed the putative transcription factor binding sites, e.g. TATA box, ERE, AP1 and CAAT box. Using luciferase as a reporter gene, we found that an estrogen response element in the promoter of RC-RNase was essential for both basic transcription and estradiol-mediated gene activation in estrogen receptor-positive MCF7 cells. These results support the hypothesis that RC-RNase is synthesized in the liver upon stimulation by estradiol during oogenesis, then secreted into the bloodstream and stored in oocytes for embryonic development.