COMMENTARY Growth regulation of the PCNA gene

The proliferating cell nuclear antigen (PCNA) is a nuclear protein of about 29000Mr, which was independently discovered by Miyachi et al. (1978) as PCNA and by Bravo and Celis (1980) as cyclin. More recently it has been identified as the co-factor of DNA polymerase delta (Prelich et al. 1987a; Bravo et al. 1987), a protein that had been previously isolated by Tan et al. (1986). Both DNA polymerases a and delta are necessary for DNA replication (Tsurimoto and Stillman, 1989). As the co-factor of DNA polymerase delta, PCNA is therefore necessary for DNA replication (Prelich et al. 1987a,6; Bravo et al. 1987). The relationship between DNA polymerase delta and PCNA has been reviewed recently by Fairman (1990). According to Stillman and co-workers PCNA is necessary for the synthesis of the leading and lagging strands of DNA (Prelich and Stillman, 1988). For its function it requires ATP, it has ATPase activity and has some homologies with gene 45 of the T4 phage (Tsurimoto and Stillman, 1990). The role of PCNA in DNA replication in vitro has been further elucidated by Tsurimoto et al. (1990).