ARTICLE

THE SYNTHESIS OF ACIDIC CHROMOSOMAL PROTEINS DURING THE CELL CYCLE OF HELA S-3 CELLS

T. W. Borun ¹ and G. S. Stein ¹

¹ From the Fels Research Institute and the Department of Pathology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140

The kinetics of acidic residual chromosomal protein synthesis and transport were studied throughout the cell cycle in HeLa S-3 cells synchronized by 2 mM thymidine block and selective detachment of mitotic cells. Pulse labeling the cells with leucine-³H for 2 min and then "chasing" the radioactive proteins for up to 3 hr showed that the amount of protein synthesized, transported, and retained in the acidic residual chromosomal protein fraction is greater immediately after mitosis and later in G₁ than in the S or G₂ phases of the cell cycle. During S, only 20–25% of the proteins synthesized and transported to the acidic residual chromosomal protein fraction are chased during the first 2 hr after pulse labeling, whereas up to 40% of the material entering the residual nuclear fraction in mitosis, G₁, and G₂ leaves during a 2 hr chase. Polyacrylamide gel electrophoretic profiles of these proteins, at various times after pulse labeling, reveal that the turnover of individual polypeptides within this fraction has kinetics of synthesis and turnover which are markedly different from one another and undergo stage-specific changes.

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This article has been cited by other articles:

• Stein, G. S., Spelsberg, T. C., Kleinsmith, L. J. (1974). Nonhistone Chromosomal Proteins and Gene Regulation: Nonhistone chromosomal proteins may participate in the specific regulation of gene transcription in eukaryotes. Science 183: 817-824 [Abstract]  
• Allfrey, V. G., Inoue, A., Karn, J., Johnson, E. M., Vidali, G. (1974). Phosphorylation of DNA-binding Nuclear Acidic Proteins and Gene Activation in the HeLa Cell Cycle. Cold Spring Harb Symp Quant Biol 38: 785-801 [Abstract]  
• Stein, G. S., Matthews, D. E. (1973). Nonhistone Chromosomal Protein Synthesis: Utilization of Preexisting and Newly Transcribed Messenger RNA's. Science 181: 71-73 [Abstract]  

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