Mechanisms of Gene Regulation
Ordiz, M. Isabel , Barbazuk, Brad , Beachy, Roger N. .
Functional analysis of the acidic domain of RF2a, a rice b-ZIP protein.
The mechanisms that control gene expression, including how transcription factors bind to a recognition sequence and interact with other transcriptional machinery are not well understood. Eukaryotic transcription factors have two general activities: a DNA binding function and a transcription activation function.
RF2a is a rice b-ZIP transcription factor that interacts with the BoxII cis element of the promoter of rice tungro bacilliform virus and enhances transcription of the viral genome. RF2a possesses three different regulatory domains: a domain rich in acidic aminoacids; a proline-rich domain; and a glutamine-rich domain. The function of the domains has been partially characterized (Dai et al., 2003).
Here we studied the role of the acidic domain in activating gene expression independent of the b-ZIP domain using two different systems. We fused the synthetic zinc finger protein ZF-TF 2C7 with the acidic domain (aminoacids 49-116) and tested its expression in transgenic Arabidopsis plants. The expression of a minimal retinoblastoma promoter linked to a reporter gene was increased up to ten times and correlated with RNA levels of both the reporter and effector genes. In transient assays with tobacco BY-2 protoplasts, we determined that the minimal activation domain comprised amino acids 56-84 (A5). This subdomain was equally as effective in activating gene expression as the full acidic domain. Using a chemically inducible system, we demonstrated that A and A5 domains increase gene expression in transgenic Arabidopsis plants up to 800 fold. Bioinformatics analysis showed that the minimal acidic domain of RF2a is present only in b-ZIP; in dicots, the A domain has an insertion that is not present in monocots.
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1 - Donald Danforth Plant Science Center, 975 N. Warson Road, St Louis, MO, 63132, USA
2 - Donald Danforth Plant Science Center
bZIP transcription factors
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM