Immunogold localization of a nuclear protein at different stages of the cell cycle in normal and tumor cells.

The interaction of immunogold particles with a specific antigen was used to localize this nuclear protein (Mr 68 kd, pI 6.5-8.2) in fetal liver cells and oesophageal carcinoma cells at different stages of the cell cycle. In interphase hepatocytes, the 68 kd antigen was localized exclusively in the nucleus and associated with both heterochromatin and euchromatin. As the chromatin condensed into chromosomes at later stages of the cell cycle, the 68 kd antigen remained closely associated with them. Similar phenomena were observed in the oesophageal carcinoma cells, suggesting that this 68 kd nuclear protein may be involved in anchoring the actively transcribed DNA and in maintaining the chromosomal architecture during the cell cycle.