Proliferating cell nuclear antigen from a basidiomycete, <i>Coprinus cinereus</i>

<jats:p>The primary purpose of the present study was to investigate whether DNA replication at meiotic prophase also requires replication factors, especially proliferating cell nuclear antigen (PCNA). We cloned <jats:italic>PCNA</jats:italic> cDNAs (<jats:italic>CoPCNA</jats:italic>) from a cDNA library made from basidia of the basidiomycete, <jats:italic>Coprinus cinereus</jats:italic>. Interestingly, although <jats:italic>CoPCNA</jats:italic> is a single‐copy gene in the genome, two different <jats:italic>PCNA</jats:italic> cDNA species were isolated using degenerate primers and a meiotic cDNA library, and were designated as <jats:italic>CoPCNA‐α</jats:italic> and <jats:italic>CoPCNA‐β</jats:italic>. <jats:italic>CoPCNA‐β</jats:italic> was made by truncating at specific sites in <jats:italic>CoPCNA‐α</jats:italic> mRNA, 5′‐AAGAAGGAGAAG‐3′ and 5′‐GAAGAGGAAGAA‐3′. Both of these sequences were present in exon IV in the genomic sequence, and interestingly the former was the same as the inverse sequence of the latter. CoPCNA‐α was 107 amino acids larger than human PCNA, and so the 107 amino‐acid sequence was inserted in a loop, the so‐called D<jats:sub>2</jats:sub>E<jats:sub>2</jats:sub> loop, in human PCNA. Northern blotting analysis indicated that <jats:italic>CoPCNA</jats:italic> was expressed not only at premeiotic S but also at the meiotic prophase stages such as leptotene and early zygotene, just before and when karyogamy occurs and the homologous chromosomes pair. Western blotting analysis using anti‐(CoPCNA‐α) Ig revealed that at least two <jats:italic>CoPCNA</jats:italic> mRNAs before and after truncation were translated at the meiotic prophase as CoPCNA‐α and CoPCNA‐β.</jats:p>