Activation of Viral and Host Gene Expression

The mastrevirus Rep and RepA proteins are implicated in activation of expression of viral late gene expression. We have shown that although the RepA protein functions as an auto activator in the yeast two-hybrid system, both Rep and RepA are required for activation of expression from the coat protein gene in plant cells. However, we have recently shown that movement protein gene expression is not activated in these cells. This provides an additional level of regulation of late gene expression, important when two proteins are produced from the same transcriptional unit. Our current investigations aim to determine the protein and DNA sequences required for activation and their importance in the mastrevirus life cycle. The RepA protein interacts with a plant retinoblastoma-like protein resulting in the release of cellular transcription factors important for cell-cycle progression. This interaction provides us with a tool for the investigation of activation of host gene expression and the control of the host cell cycle. These studies require the use of transient and stable gene expression analyses, cell biological, and microarray technologies.

Vascular specific GUS activity in leaves of rice plants transformed with the gus gene expressed from the MSV coat protein promoter