Abstract
Nuclear acidic proteins solubilized from young and senescent human diploid fibroblasts were analyzed by two-dimensional gel electrophoresis. The age-related increase in nuclear proteins was due mainly to the accumulation of residual acidic proteins. Differences in seven major nuclear acidic proteins between young and senescent cells were observed. [35S]-menthionine autoradiography showed that senescent cells had lost the ability to synthesize detectable amounts of four major proteins that are found in young cells. In addition, senescent cells synthesized two new major proteins that were undetectable in young cells. The isoelectric point of a single polypeptide with the molecular weight 37, 000 seemed to shift from 5.3 to 5.8 with cellular aging.
