Effects of RNase L mutations associated with prostate cancer on apoptosis induced by 2',5'-oligoadenylates.
The RNASEL gene, a strong candidate for the hereditary prostate cancer 1 allele (HPC1), encodes a single-stranded specific endoribonuclease involved in the antiviral actions of IFNs. RNase L is activated enzymatically after binding to unusual 5'-phosphorylated, 2',5'-linked oligoadenylates (2-5A). Biostable phosphorothioate analogues of 2-5A were synthesized chemically and used to study the effects of naturally occurring mutations and polymorphisms in RNASEL. The 2-5A analogues induced RNase L activity and caused apoptosis in cultures of late-stage, metastatic human prostate cancer cell lines DU145, PC3, and LNCaP. However, DU145 and PC3 cells were more sensitive to 2-5A than LNCaP cells, which are heterozygous for an inactivating deletion mutation in RNase L. The RNase activities of missense variants of human RNase L were compared after expression in a mouse RNase L(-/-) cell line. Several variants (G59S, I97L, I220V, G296V, S322F, Y529C, and D541E) produced similar levels of RNase L activity as wild-type enzyme. In contrast, the R462Q variant, previously implicated in up to 13% of unselected prostate cancer cases, bound 2-5A at wild-type levels but had a 3-fold decrease in RNase activity. The deficiency in RNase L(R462Q) activity was correlated with a reduction in its ability to dimerize into a catalytically active form. Furthermore, RNase L(R462Q) was deficient in causing apoptosis in response to 2-5A consistent with its possible role in prostate cancer development. Our findings support the notion that RNASEL mutations and some variants allow tumor cells to escape a potent apoptotic pathway.
Xiang
Ying
Y
Department of Cancer Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Wang
Zhengfu
Z
Murakami
Junko
J
Plummer
Sarah
S
Klein
Eric A
EA
Carpten
John D
JD
Trent
Jeffrey M
JM
Isaacs
William B
WB
Casey
Graham
G
Silverman
Robert H
RH
D000227:Adenine Nucleotides / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D001859:Bone Neoplasms / Q000556:secondary; D001932:Brain Neoplasms / Q000556:secondary; D045744:Cell Line, Tumor; D019281:Dimerization; D004722:Endoribonucleases / Q000235:genetics*; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D020125:Mutation, Missense; D009843:Oligoribonucleotides / Q000494:pharmacology*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics / Q000473:pathology
D000227:Adenine Nucleotides; D009843:Oligoribonucleotides; C023505:2',5'-oligoadenylate; D004722:Endoribonucleases; C031956:2-5A-dependent ribonuclease