PROTEIN-SYNTHESIS AND PROTEIN-DEGRADATION THROUGH THE CELL-CYCLE OF HUMAN NHIK 3025 CELLS INVITRO

The rates of protein synthesis and protein degradation through the cell cycle of human NHIK 3025 cells in balanced growth were studied in cells synchronized by mitotic selection. The rates of protein synthesis and protein degradation per cell were found to increase smoothly from the first measurements after selection (mitosis) and until the beginning of the next mitosis. By the end of the cell cycle, both the rate of protein synthesis per cell and the rate of protein degradation per cell had doubled their values relative to the extrapolated values at the beginning of the cell cycle. The increase in the rates of protein synthesis and protein degradation seemed to follow the increase in total protein content closely, i.e. the rates of protein synthesis and protein degradation given as percentage of total protein were constant throughout the cell cycle of NHIK 3025 cells in balanced growth. The rate of protein accumulation, either measured directly or calculated as the difference between the rates of protein synthesis and protein degradation, allowed for a doubling of the protein content during the median time period required to complete the cell cycle. © 1979.