Uridine uptake and its intracellular phosphorylation during the cell cycle

✍ Scribed by Peter J. Stambrook; James D. Ebert; Jesse E. Sisken

• Publisher: John Wiley and Sons
• Year: 1973
• Tongue: English
• Weight: 685 KB
• Volume: 82
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1040820215

✦ Synopsis

Abstract

The rate of 5‐^3^H uridine uptake into Chinese hamster V79 cells and the rate of its incorporation into RNA increase tenfold during the cell cycle. Both reactions exhibit the same apparent K~m~(1.7 × 10^−5^ M). Chromatography of acid‐soluble material from cells incubated with 5‐^3^H uridine (0.25 μM) at different times of the cell cycle revealed that intracellular uridine was rapidly phosphorylated at all times, even though cells in late S and G~2~ take up roughly ten times as much uridine as cells in G~1~. Uridine kinase activity in synchronized cells increases about two and one‐half‐fold during the same time period, and in exponentially growing cells is not saturated until the external uridine concentration is raised above 200 μM. It is concluded that the change in uridine kinase activity during the cell cycle is not responsible for the tenfold increase in the rate of uridine transport, and that these two processes are independently regulated.