Molecular characterisation and stage-specific expression of proliferating cell nuclear antigen (PCNA) from the malarial parasite,Plasmodium falciparum

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Abstract
The gene encoding the malarial homologue of proliferating cell nuclear antigen, PCNA, has been Identified and characterised. it is located on chromosome 13. The coding sequence of 825 nucleotides predicts a protein of 30,586 Da. There are no introns and northern analysis reveals a transcript of 1.6kb. The conserved residues which characterise the PCNAs of human, Drosophila, Saccharomyces and Xenopus are present In PfPCNA but the overall Identity of PfPCNA with human and yeast PCNAs is low; 34% and 31% respectively. PfPCNA Is longer than the PCNAs of these other species by about 16 amino adds, most of which are present in a block near the carboxy terminus. Antibodies against a purified PfPCNA glutathlone-S-transferase fusion protein recognise a single band in western blots of parasite extracts at 32kDa. The same antlserum has been used to demonstrate that the expression of PfPCNA Is regulated during the Intraerythrocytlc development of the parasite. Expression Increases dramatically In late trophozoites and Is maintained during the subsequent nuclear divisions which produce schlzonts.