DNA引发酶负责引物合成，在DNA复制过程中起关键作用。极端嗜热古菌-硫化叶菌中的真核生物类型引发酶PriSL（由催化亚基PriS和非催化亚基PriL组成的异二聚体）被认为是参与DNA复制的引发酶。但该酶在体外生化实验中仅表现很弱的引物合成活性。本实验室最近发现，硫化叶菌的一个功能未知蛋白（命名为PriX）能够辅助引发酶催化亚基PriS高效合成引物，提示可能存在新的引物合成体系PriS/PriX。本项目拟以冰岛硫化叶菌为主要材料、采用生物化学、遗传学、结构生物学等手段，围绕PriX，系统研究PriS/PriX的生化性质、亚基相互作用、生理功能及调控机制，阐释其在DNA复制过程中的作用。本项目的实施将改变对古菌中参与DNA复制的引发酶的认识，丰富关于引发酶进化规律和生理功能分化的知识。

DNA primase serves a key role in DNA replication. The eukaryotic-type heterodimeric DNA primase PriSL is believed to be responsible for primer synthesis in hyperthermophilic archaea of Sulfolobus. However, PriSL exhibits very low activity in primer synthesis in vitro. Our laboratory has recently found that a functionally unkown protein, denoted PriX, is capable of promoting highly efficient primer synthesis by PriS, suggesting the existence of a novel priming mechanism. This project will systematically investigate the biochamical properties, subunit interaction, physiological function and regulation of PriX and PriS/PriX in Sulfolobus islandicus by employing biochemical, genetic and structural biological approaches to understand the role of the enzyme in DNA replication. The successful execution of the project may lead to a change in our view on primases functioning in archaeal DNA replication and a better knowledge of the evolution and functional divergence of primases.