The two-dimensional polypeptide profile of terminally non-dividing human diploid cells

We have used high resolution two-dimensional polyacrylamide gel electrophoresis (PAGE) to compare the polypeptides synthesized by normal human diploid fibroblasts cells which have significant proliferative capacity with those of cells which are terminally non-dividing. Normal cells that are terminally non-dividing (i.e., have no remaining proliferative potential) synthesize two polypeptides that are not detected in young cells which are either actively proliferating or growth arrested by incubation in medium containing a low concentration of serum (0.3%) for 72 h. Continued maintenance of young cells in the growth-arrested state ultimately leads to the detectable synthesis of one of the polypeptides synthesized by terminally non-dividing cells. Some preliminary biochemical properties of these two polypeptides are examined.