Transfer RNA(4lys) and cell cycle progression: characterization of ts-694 cells.
Lysine tRNA modification has been studied in mammalian ts-694 cells with respect to cell cycle progression in temperature downshift and upshift experiments. The modification of tRNA(lys) measured in temperature downshift experiments showed that tRNA(4lys) levels start to increase 6 h following the temperature shift, approximately 10-12 h prior to the cells entry into S phase. Ts-694 cells showed a gradual decrease in the level of tRNA(4lys) and the rates of DNA synthesis following a temperature upshift. The cells became growth arrested following incubation for 36-45 h at the rt. Cell cycle mapping of the temperature restriction point suggests a G1 block prior to the serum deprivation restriction point. Depletion of cellular tRNA(4lys) by serum deprivation followed by simultaneously shifting cells to the rt and feeding medium containing 10% serum showed that cells with low tRNA(4lys) levels and no mechanism for the synthesis of tRNA(4lys) could not enter S phase and synthesize DNA. Blocking of ts-694 at the G1/S boundary with aphidicolin indicates that cells that have passed through G1 are capable of entering S phase and synthesizing DNA independent of the incubation temperature. These results indicate that tRNA(4lys) is not needed during S phase for DNA replication but suggests that tRNA(4lys) is required for cells to progress through G1.
Turchi
J J
JJ
Department of Biochemistry, University of Missouri, Columbia 65212.
Weisman
G A
GA
Ortwerth
B J
BJ
D000818:Animals; D002453:Cell Cycle; D002455:Cell Division; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D012357:RNA, Transfer, Lys / Q000378:metabolism*; D013696:Temperature
D012357:RNA, Transfer, Lys; D004247:DNA