Abstract
The RPC-5 chromatographic profiles of lys-tRNA were analyzed during the growth of 3T3 cells in culture. An inverse relationship was seen between tRNA 2 lys and tRNA 4 lys which was markedly influenced by medium changes. This interchange of tRNA 2 lys and tRNA 4 lys could be controlled by altering the levels of serum in the medium, or more precisely by altering the serum to cell ratio. A different change in lys-tRNA distribution was seen when the cells reached confluency. The amounts of tRNA 2 lys, tRNA 3 lys and tRNA 4 lys all decreased with a corresponding increase in either tRNA 5 lys or tRNA 6 lys. An identical change in lys-tRNA could be produced by shifting sparse cells into a medium containing 10% calf plasma instead of 10% serum. Both tRNA lys profiles and cell growth were returned to normal when the cells were returned to medium with 10% fetal calf serum (FCS) or 10% calf plasma and fibroblast growth factor (FGF). A third alteration in tRNA lys profiles was seen by the addition of cAMP to the cultures. A decrease in tRNA 5 lys and a corresponding increase in tRNA 6 lys was seen upon the addition of 10 −3 M db-cAMP and was accentuated by the simultaneous addition of 10 −3 M methyl isobutylxanthine. These data are consistent with an ordered sequence of tRNA lys modification involving tRNA 2 lys, tRNA 3 lys, tRNA 4 lys, tRNA 5B lys and tRNA 6 lys. Several of the factors which control proliferation appear to control the activity of different tRNA-modifying enzymes in this tRNA lys pathway thereby controlling the levels of tRNA 4 lys, a tRNA previously shown to correlate directly with the proliferative rate of cells.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call