Protein Targeting and Vesicular Trafficking
Ali, Gul , Reddy, Anireddy S. N. .
Nuclear and Speckle targetting Signals in a Plant Splicing Factor: Regulation of Intranuclear Mobility by ATP, Phosphorylation and Transcription.
Pre-mRNA splicing takes place in a spliceosome that consists of five small ribonucleoprotein particles (snRNPs) and a large number of non-snRNP splicing factors. The serine/arginine-rich (SR) proteins, a family of non-snRNP proteins, function at multiple steps in the assembly of the spliceosome in non-plant systems. Limited studies with metazoan SR splicing factors (ASF/SF2 and SC35) indicated that their mobility is not dependent on ATP and phosphorylation. Here we analyzed the mobility of SR45, a plant-specific SR protein with unique domain organization, and SR1/SRp34, a plant homolog of metazoan ASF/SF2, using fluorescence recovery after photobleaching (FRAP) and fluorescence loss in photobleaching (FLIP). In contrast to metazoan SR splicing factors the movement of the plant SR proteins is dependent on ATP, phosphorylation and transcription. To understand the underlying mechanism for these observations, we first analyzed the signals necessary for nuclear and speckle localization of SR45 with GFP-tagged deletion mutants. These studies have revealed that the nuclear localization signals are located in arg/ser-rich domains (RS) 1 and 2, whereas the speckle targeting signals are exclusively present in RS2. Using the same deletion mutants, we carried out mobility analyses in the presence of inhibitors of transcription or phosphorylation. These analyses show that the sensitivity of SR45 to these inhibitors is conferred by an RNA recognition motif (RRM) and the RS2 domain. Overall, these results suggest fundamental differences in the regulation of the mobility of plant and animal SR splicing factors. A model on the regulation of SR45 mobility between nucleoplasm and speckles under different physiological states will be presented.
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1 - Colorado State University, Department of Biology and Program in Cell and Molecular Biology, Biology-1878, Fort Collins, CO, 80523, USA
2 - Colorado State Univerity, Department of Biology and Program in Cell and Molecular Biology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM