Initiation of Geminivirus DNA Replication

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9506038 Hanley-Bowdoin Geminiviruses constitute a unique family of eucaryotic DNA viruses with single-stranded genomes that replicate through a rolling circle mechanism in the nuclei of infected plant cells. They have small genomes, encode one protein that is essential for their replicatoin, and recruit the replication machineryof their hosts. These features make geminiviruses excellent model systems for studying eucaryotic DNA replication, an area of study that has not been pursued extensively in plant systems. Study of plant DNA replication and its integration into the cell division cycle will provide valuable insight into the universal mechanisms that underlie these processes in all organisms and may reveal important differences that are responsible for the fundamentally different developmental pathways of plants and animals. This research will study the events that lead to initiation of geminivirus replication, and will provide a rare opportunity to examine the mechanism of rolling circle replication in a eucaryotic system. It will also from the foundation of our long term research goals to identify and understand the functions of host proteins in geminivirus and plant nuclear DNA replication. The well-characterized geminivirus, tomato golden mosaic virus (TGMV), will be used for these experiments. The TGMV replication origin has been mapped to an 89-bp sequence. TGMV encodes two proteins for its replication one (AL1) that is absolutely required and a second (AL3) that impacts viral DNA accumulation. The objectives of this research are to examine the sequence and structural requirements for function of a geminivirus minimal origin of replication, to characterize the functions of an essential geminivirus replication protein, to characterize the steps leading to initiation of geminivirus replication. %%% Geminiviruses constitute a unique family of eucaryotic DNA viruses with single-stranded genomes that replicate through a rolling circle mechanism in the nuclei of infected plant ce lls. They have small genomes, encode one protein that is essential for their replicatoin, and recruit the replication machineryof their hosts. These features make geminiviruses excellent model systems for studying eucaryotic DNA replication, an area of study that has not been pursued extensively in plant systems. The goal of this research is to understand the molecular processes that mediate geminivirus replication and to relate these events to plant nuclear DNA replication. Study of plant DNA replication and its integration into the cell division cycle will provide valuable insight into the universal mechanisms that underlie these processes in all organisms and may reveal important differences that are responsible for the fundamentally different developmental pathways of plants and animals. ***