Gene for proliferating-cell nuclear antigen (DNA polymerase delta auxiliary protein) is present in both mammalian and higher plant genomes.

Abstract

Proliferating-cell nuclear antigen (PCNA; also called cyclin) was originally described in proliferating mammalian cells as a nuclear protein with an apparent Mr of 33,000-36,000 and recently was found to be a DNA polymerase 6 auxiliary protein.To elucidate whether PCNA/cyclin is a universal protein necessary for proliferation of eukaryotes, a search was conducted for PCNA/cyclin homologues in higher plants. In Southern blot-hybridization analysis, a rat PCNA/ cyclin cDNA probe hybridized with homologous sequences in genomic DNAs from rice, soybean, and tobacco. A PCNA/ cyclin-related molecular clone (pCJ-1) was isolated from rice DNA and was partially sequenced. The pCJ-1 probe hybridized with a 1.2-kilobase transcript in RNA from rice root tips and shoots. Immunoblot analysis of the soluble extract of soybean root tips with monospecific anti-PCNA/cycin identified an immunoreactive protein with an apparent Mr of 34,000.Immunohistochemical analysis revealed the presence of an immunoreactive PCNA/cyclin protein in the nuclei of cells in the meristem of soybean root tips. The highly homologous nature of the gene for PCNA/cyclin throughout the animal and plant kingdoms suggests that the product of the gene plays an essential role in DNA replication in eukaryotes.Proliferating-cell nuclear antigen (PCNA; also called cyclin) has received considerable attention in recent years because it has been demonstrated to be identical to DNA polymerase 8 auxiliary protein (1, 2), which is required for the polymerase to copy templates such as poly(dA)/oligo(dT), primed M13 DNA, and denatured calf thymus DNA. DNA polymerase 8 (3-5) differs from other mammalian DNA polymerases such as DNA polymerases a, f3, and y by having an exonuclease activity. Since the exonuclease activity is in the 3'-5' direction, DNA polymerase 8 has a proofreading activity (6), as seen with the prokaryotic DNA polymerases (7), and is expected to play a significant role in the maintenance of the fidelity of mammalian DNA replication (6). From the studies on molecularly cloned cDNA for PCNA/cyclin (8-10) and on the antigenicity of PCNA/cyclin (11,12), it has been recognized that this protein may be similar among a wide range of higher eukaryotes and, thus, conserved during evolution. The deduced amino acid sequences from rat (8, 9) and human (10) PCNA/cyclin cDNAs reveal only 4 amino acid substi- MATERIALS AND METHODS Plant Materials. Two rice subspecies (Indica and Japonica of Oriza sativa L.), soybean (Glycine max Merril), and tobacco (Nicotiana tabacum L.) were used. The cultivars of Japonica rice used were Musashikogane, Taichung 65, Nipponbare, and Sasanishiki.Labeling of DNA Probe. The rat PCNA/cyclin cDNA, pCR-1 (8, 9), was used. The Pst I digest of the pCR-1 insert yielded two bands in addition to the plasmid DNA in gel electrophoresis. The larger fragment (0.75 kb) contains 88% of the coding region of rat PCNA/cyclin cDNA and was used as a hybridization probe (pCR-1 probe). The probe was radiolabeled to a specific activity of 1 x 109 cpm/,ug...

Isolation and characterization of cDNA clones for plant cyclins.

“…We have isolated and characterized both genomic clones and cDNAs for plant proliferating cell nuclear antigen (PCNA, an auxiliary protein of DNA polymerase 6; this should not be confused with cyclins (Suzuka et al, 1989(Suzuka et al, , 1991. It has also been reported that plants have p34cdc2 or related proteins (John et al, 1989;Feiler and Jacobs, 1990;Hata, 1991).…”

Immunohistochemistry in diagnostic veterinary pathology: a critical review

“…Amino acid sequences of proliferating cell nuclear antigen (PCNA) present high homology among mammalians, and also in superior vegetal (28) . In our cases, nuclear reactivity for PCNA was strong, with faint cytoplasmic staining in mitotic cells (12,34) .…”

Regulating DNA Replication in Plants

“…PCNA is an essential protein, highly conserved in all eukaryotes, including plants (Suzuka et al 1989;Kodama et al 1991;Hata et al 1992;Matsumoto et al 1994;Lopez et al 1995;Shimizu and Mori 1998;Strzalka et al 2010). It is frequent that plant genomes contain two PCNA genes, in contrast to PCNA pseudogenes normally found in mammalian cells.…”