PSL, AN S-PHASE-RELATED P55 NUCLEAR ANTIGEN, ASSOCIATES TRANSIENTLY WITH CHROMATIN

An S phase-related nuclear 55K antigen, also designated PSL, was characterized in various mammalian cells, using a human serum from a patient with autoimmune disorders (Barque et al 1983). In this report immunoelectron microscopy showed that the p55 protein associates in situ with the chromatin of rat hepatocytes. This association is a transient one, as indirect immunofluorescence studies show that PSL does not bind to individualized metaphase chromosomes. Immunoprecipitation tests indicate that the majority of PSL is in the nonchromosomal cell fraction. These results suggest that this nuclear antigen is directly involved in the DNA replication process.