De Novo DNA Synthesis by Yeast DNA Polymerase I Associated with Primase Activity
DNA synthesis at the replication fork is carried out continuously on the leading-strand and discontinuously on the lagging-strand (1). The nascent DNA chains (Okazaki fragments) on the lagging-strand are synthesized by elongation of RNA initiators. Primase, the product of dnaG gene, synthesizes short ribo- or mixed ribodeoxyribo-oligonucleotide which are elongated by DNA polymerase III holoenzyme during the replication of the Escherichia coli chromosome and priming activities are also involved in the replication of several bacteriophage genomes (1). A similar activity has been implicated in the initiation of Okazaki fragments during the semidiscontinuous replication of polyoma DNA in intact nuclei (2), and some very recent reports have suggested that DNA primase activity may be associated with DNA polymerase a from eukaryotic organisms (3–6). The budding yeast Saccharomyces cervisiae contains two non-mitochondrial DNA polymerases, named DNA polymerase I and II (7–9). DNA polymerase I is the major enzyme and has biochemical properties similar to those of eukaryotic DNA polymerase a. DNA polymerase II resembles pro-karyotic DNA polymerases because of the presence of an associated proofreading 3’-exonuclease.
KeywordsReplication Fork High Molecular Weight Form Okazaki Fragment Primase Activity dnaG Gene
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