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A DNA sequence required for geminivirus replication also mediates transcriptional regulation
P A Eagle1, B M Orozco, L Hanley-Bowdoin
1Department of Biochemistry, North Carolina State University, Raleigh 27695-7622.
The Plant Cell
|August 1, 1994
Summary
The Tomato golden mosaic virus replication protein (AL1) represses its own promoter activity by binding to a specific DNA sequence. This transcriptional repression is independent of viral DNA replication.
Area of Science:
- Molecular Biology
- Plant Virology
- Gene Regulation
Background:
- Geminiviruses, like Tomato golden mosaic virus (TGMV), rely on virus-encoded proteins for replication.
- The TGMV replication protein, AL1, is known to bind a specific DNA sequence crucial for replication origin activity.
Purpose of the Study:
- To investigate the role of the TGMV AL1 protein in transcriptional regulation.
- To determine if the AL1 binding site involved in replication also mediates transcriptional repression.
- To explore the relationship between TGMV transcriptional repression and DNA replication.
Main Methods:
- Analysis of AL1 binding site mutants using transient expression assays.
- Introduction of the AL1 binding site into a heterologous promoter (Cauliflower mosaic virus 35S promoter).
- Studies using truncated AL1 promoters, mutant AL1 proteins, and different Nicotiana cell lines.
Main Results:
- The AL1 binding site essential for replication also mediates transcriptional repression of the TGMV promoter.
- Transcriptional repression by AL1 does not require a replication-competent template or AL1 protein.
- Different Nicotiana cell lines exhibited varying levels of AL1-mediated repression, suggesting cell-specific factors.
Conclusions:
- The TGMV AL1 protein functions as a transcriptional repressor of its own promoter.
- Geminivirus transcriptional repression and DNA replication appear to be independent processes.
- Cellular factors influence the efficiency of geminivirus-mediated transcriptional repression.