TY - JOUR
T1 - Catalytic cleavage of the androgen receptor messenger RNA and functional inhibition of androgen receptor activity by a hammerhead ribozyme
AU - Chen, S.
AU - Song, C. S.
AU - Lavrovsky, Y.
AU - Bi, B.
AU - Vellanoweth, R.
AU - Chatterjee, B.
AU - Roy, A. K.
PY - 1998
Y1 - 1998
N2 - Androgen receptor (AR) plays a key role in cell growth both in the normal prostate and in prostate cancer. Androgen ablation and prolonged antiandrogen therapy can give rise to AR-dependent prostate tumors, which nonetheless can grow in the androgen-deprived milieu. Here we describe the ribozyme approach to selectively degrading the AR mRNA and thereby inhibiting AR function. A trans-acting hammerhead ribozyme was designed to cleave the rat AR mRNA at the position +1827/ 1828, a region predicted to be minimally involved in generating stable secondary structures. Using AR mRNA fragments as substrates, it was established that this ribozyme can specifically cleave the RNA target in a sequence-specific manner. Kinetic experiments determined a K(m) for the substrate of 77 nM and a k(cat)/K(m) value of 1.8 x 107 M-1, min-1, suggesting a catalytic efficiency similar to that of protein enzymes such as the relatively nonspecific ribonuclease A and a sequence-specific endonuclease EcoRI. Transient cotransfections of prostate-derived PC3 cells with three plasmids, an AR-inducible chloramphenicol acetyltransferase (CAT) reporter, an AR expression vector, and a ribozyme expression vector, showed that the ribozyme was capable of reducing the functional activity of AR. At an equimolar ratio of the AR expression plasmid to ribozyme expression plasmid, androgen-inducible CAT activity was inhibited 70%. Similar extents of inhibition were also observed at the cellular mRNA level using ribonuclease protection assays, indicating that the ribozyme functioned as an AR mRNA cleaving enzyme in cellulo. Immunocytochemical examination revealed a decline of AR immunoreactivity in ribozyme-transfected cells. In addition, no morphologically detectable cellular abnormalities were associated with ribozyme expression, indicating the absence of deleterious side effects. These results offer a new avenue for the control of AR function and cell growth, especially in the case of androgen-resistant, but AR-dependent, prostate cancer cells.
AB - Androgen receptor (AR) plays a key role in cell growth both in the normal prostate and in prostate cancer. Androgen ablation and prolonged antiandrogen therapy can give rise to AR-dependent prostate tumors, which nonetheless can grow in the androgen-deprived milieu. Here we describe the ribozyme approach to selectively degrading the AR mRNA and thereby inhibiting AR function. A trans-acting hammerhead ribozyme was designed to cleave the rat AR mRNA at the position +1827/ 1828, a region predicted to be minimally involved in generating stable secondary structures. Using AR mRNA fragments as substrates, it was established that this ribozyme can specifically cleave the RNA target in a sequence-specific manner. Kinetic experiments determined a K(m) for the substrate of 77 nM and a k(cat)/K(m) value of 1.8 x 107 M-1, min-1, suggesting a catalytic efficiency similar to that of protein enzymes such as the relatively nonspecific ribonuclease A and a sequence-specific endonuclease EcoRI. Transient cotransfections of prostate-derived PC3 cells with three plasmids, an AR-inducible chloramphenicol acetyltransferase (CAT) reporter, an AR expression vector, and a ribozyme expression vector, showed that the ribozyme was capable of reducing the functional activity of AR. At an equimolar ratio of the AR expression plasmid to ribozyme expression plasmid, androgen-inducible CAT activity was inhibited 70%. Similar extents of inhibition were also observed at the cellular mRNA level using ribonuclease protection assays, indicating that the ribozyme functioned as an AR mRNA cleaving enzyme in cellulo. Immunocytochemical examination revealed a decline of AR immunoreactivity in ribozyme-transfected cells. In addition, no morphologically detectable cellular abnormalities were associated with ribozyme expression, indicating the absence of deleterious side effects. These results offer a new avenue for the control of AR function and cell growth, especially in the case of androgen-resistant, but AR-dependent, prostate cancer cells.
UR - http://www.scopus.com/inward/record.url?scp=0032230278&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032230278&partnerID=8YFLogxK
U2 - 10.1210/mend.12.10.0186
DO - 10.1210/mend.12.10.0186
M3 - Article
C2 - 9773979
AN - SCOPUS:0032230278
SN - 0888-8809
VL - 12
SP - 1558
EP - 1566
JO - Molecular Endocrinology
JF - Molecular Endocrinology
IS - 10
ER -