Inhibition of human telomerase by rubromycins: implication of spiroketal system of the compounds as an active moiety.
We found that a group of rubromycins and their analogues, a class of quinone antibiotics that possesses benzofuran and benzodipyran rings to form a spiroketal system, strongly inhibited human telomerase as assessed with a modified telomeric repeat amplification protocol. beta- and gamma-Rubromycins and purpuromycin appeared to be the most potent telomerase inhibitors, with 50% inhibitory concentrations (IC(50)) of about 3 microM, and griseorhodins A and C also showed comparable potencies for the inhibition (IC(50) = 6-12 microM). In contrast, opening of the spiroketal system of beta-rubromycin, giving rise to alpha-rubromycin, substantially decreased its inhibitory potency toward telomerase (IC(50) > 200 microM), indicating the essential role of the spiroketal system in telomerase inhibition. A kinetic study of the inhibition by beta-rubromycin revealed a competitive interaction with respect to the telomerase substrate primer, with a K(i) of 0.74 microM, whereas a mixed type inhibition was observed with respect to the nucleotide substrate. beta-Rubromycin was also potent in inhibiting retroviral reverse transcriptases but had virtually no effect on other DNA/RNA-modifying enzymes including DNA and RNA polymerases, deoxyribonuclease, and topoisomerase. Although beta-rubromycin showed nonspecific cytotoxicities, reducing proliferation of cancer cells (IC(50) approximately 20 microM), we conclude that beta-rubromycin appears to be a lead structure for the development of more potent and selective inhibitors of human telomerase.
Ueno
T
T
Pharmaceuticals & Biotechnology Laboratory, Japan Energy Corporation, Toda-shi, Saitama, 335-8502 Japan.
Takahashi
H
H
Oda
M
M
Mizunuma
M
M
Yokoyama
A
A
Goto
Y
Y
Mizushina
Y
Y
Sakaguchi
K
K
Hayashi
H
H
D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006131:Growth Inhibitors / Q000737:chemistry / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D020014:K562 Cells; D009285:Naphthoquinones / Q000737:chemistry / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011809:Quinones / Q000737:chemistry* / Q000494:pharmacology / Q000633:toxicity; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry* / Q000494:pharmacology / Q000633:toxicity; D013141:Spiro Compounds / Q000737:chemistry* / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013379:Substrate Specificity / Q000187:drug effects; D019098:Telomerase / Q000037:antagonists & inhibitors* / Q000378:metabolism
D000900:Anti-Bacterial Agents; D000970:Antineoplastic Agents; D006131:Growth Inhibitors; D009285:Naphthoquinones; D011809:Quinones; D018894:Reverse Transcriptase Inhibitors; D013141:Spiro Compounds; C018070:griseorhodins; C064946:alpha-rubromycin; C064947:beta-rubromycin; C064949:gamma-rubromycin; C009115:purpuromycin; D019098:Telomerase