Inhibitory mechanisms of 1-(3-C-ethynyl-beta-D-ribopentofuranosyl)uracil (EUrd) on RNA synthesis.
1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)uracil (EUrd) is an antimetabolite that strongly inhibits RNA synthesis and shows a broad antitumor activity in vitro and in vivo. In mouse mammary tumor FM3A cells, EUrd is sequentially phosphorylated to its 5'-triphosphate, EUTP, a major metabolite, and the RNA synthesis is inhibited proportionally to its intracellular accumulation. To study the inhibitory mechanisms of EUrd on RNA synthesis, we have performed the kinetic analysis of EUTP on RNA polymerization using isolated nuclei RNA synthesis was inhibited competitively by EUTP. The inhibition constant, Ki was much lower than the Km value of UTP (Ki value of EUTP, 84 nM; Km value of UTP, 13 microM), indicating that the high affinity of EUTP could contribute to the specific inhibition of RNA synthesis. As a result of RNA synthesis inhibition, EUrd, but not ara-C, induced shrinkage of nucleoli, which are the main sites for RNA synthesis in FM3A cells. Thus, the strong affinity of EUTP to RNA polymerase and specific inhibition of RNA synthesis could contribute to its antitumor effect. EUrd is expected to be a new antitumor drug, possessing a strong inhibitory effect on the synthesis of RNA.
Yokogawa
Tatsushi
T
Faculty of Pharmaceutical Sciences, Okayama University, Okayama, Japan.
Naito
Tomoharu
T
Kanda
Hiroshi
H
Takatori
Satoshi
S
Takenaka
Kiyoko
K
Sasaki
Takuma
T
Matsuda
Akira
A
Fukushima
Masakazu
M
Kim
Hye-Sook
HS
Wataya
Yusuke
Y
D000818:Animals; D045744:Cell Line, Tumor; D005260:Female; D007700:Kinetics; D051379:Mice; D019384:Nucleic Acid Synthesis Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D012313:RNA / Q000096:biosynthesis* / Q000378:metabolism; D014529:Uridine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology
C103085:1-(3-C-ethynylribopentofuranosyl)uracil; D019384:Nucleic Acid Synthesis Inhibitors; D012313:RNA; D014529:Uridine