Functional Analysis of Pea Chloroplast DNA Polymerase and its Accessory Proteins

Abstract

Replication of DNA is a universal process occuring in all the living organisms for the duplicaton of the genetic material. The complex process requires activity of multiprotein complexes for accurate and faithful replication of the genome (Kornberg and Baker 1992, Onrust et al 1995). The replicative DNA polymerases are the key enzymes that elongate the DNA chain. These DNA polymerases are assisted by a group of accessory proteins or factors for processive, rapid, accurate and efficient DNA synthesis. A number of such accessory proteins are well characterized from animal, bacterial and yeast systems. PCNA (Proliferating cell nucler antigen), RFC (Replication factor C) and RPA (Replication factor A) and their functional analogues are three of the most extensively studied accessory proteins (Hubscher et al 1996, Tsurimoto and Stillman 1989). As eukaryotes have organelles containing their own genetic material, the duplication of this orgenellar DNA becomes essential as these organelles (like mitochondria, chloroplasts etc.) are indispensable for any eukaryotic cell. Therefore, accurate DNA replication of the organellar DNA is essential (Day and Ellis 1984). The study on the organellar DNA replication has remained focussed mainly on the animal mitochondria. Such studies have generated a lot of knowledge in relation to the various DNA polymerases (Ropp and Copeland 1996, Lewis et al 1996, Ye et al 1996) and their accessory proteins.