Human autoimmune sera specific for proliferating cell nuclear antigen (PCNA)/cyclin (auxiliary protein for DNA polymerase delta) demonstrated the presence of epitopes within the macro- and micronuclei of the hypotrichous ciliated protozoa Euplotes eurystomus. Tightly bound PCNA/cyclin was localized at the site of DNA synthesis in macronuclei, the rear zone of the replication band. Starvation or heat shock, conditions that reduce macronuclear replication, resulted in a decrease of PCNA/cyclin in replication bands. Micronuclei also exhibited PCNA/cyclin localization which persisted for a large proportion of the vegetative cell cycle and exhibited significant resistance to adverse culture conditions. Immunoprecipitation of 35S-labeled soluble Euplotes proteins with PCNA/cyclin autoimmune sera revealed a spectrum of low molecular mass proteins. PCNA/cyclin-like proteins have now been observed in the widely divergent species: human, rat, amphibian, yeast, and ciliated protozoa.
Proliferating cell nuclear antigen/cyclin in the ciliate Euplotes eurystomus: localization in the replication band and in micronuclei.
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D E Olins, A L Olins, L H Cacheiro, E M Tan; Proliferating cell nuclear antigen/cyclin in the ciliate Euplotes eurystomus: localization in the replication band and in micronuclei.. J Cell Biol 1 October 1989; 109 (4): 1399–1410. doi: https://doi.org/10.1083/jcb.109.4.1399
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