Minisymposium 19: Mechanisms of Gene Regulation
Add
this abstract to my Itinerary
Abs #
M1901: Unhypusinated Arabidopsis senescence eIF5A negatively regulates a putative ubiquitin C-terminal hydrolase gene
|
|
Presenter: |
Wang, TzannWei Contact Presenter |
Authors | Wang, TzannWei (A) Liu, Zhongda (A) Tsai, Meng-Ju Burke (A) Thompson, Thompson E (A) | | Affiliations: |
(A): University of Waterloo
|
|
|
Deoxyhypusine synthase mediates the first of two enzymatic reactions that convert inactive eukaryotic translation initiation factor 5A (eIF5A) to an activated form by modifying a conserved lysine to hypusine. The modified eIF5A is thought to facilitate selective mRNA translocation from the nucleus to the cytoplasm. To prevent hypusination, the conserved lysine of Arabidopsis-senescence-eIF5A (AteIF5A1) was mutated to alanine. Transgenic plants over-expressing AteIF5A1lysine-->alanine exhibited delayed bolting, delayed leaf senescence, bigger rosette leaves and enhanced overall stature, consistent with previous observations indicating that hypusinated eIF5A1 is required for senescence. GST-unhypusinated AteIF5A1 fusion protein produced in E. coli was employed to bind EcoRI digested Arabidopsis genomic DNA. GST-AteIF5A1-bound DNA fragments were subcloned. Thirteen different fragments were obtained and sequenced. One of these proved to be a 98-bp DNA fragment corresponding to putative ubiquitin C-terminal hydrolase (UCH). Four overlapping regions of the original 98-bp fragment were tested for binding to unhypusinated AteIF5A1 using a gel-shift assay. Only a 22-bp fragment corresponding to the region between the end of first intron and the beginning of the second exon of UCH bound unhypusinated AteIF5A1. Constitutive antisense suppression of Arabidopsis UCH in transgenic plants gave rise to a phenotype that matched the phenotype of plants over-expressing AteIF5A1lysine-->alanine, viz., delayed bolting, delayed rosette senescence and enhanced overall stature. The results are consistent with the view that unhypusinated eIF5A1 is a negative regulator of UCH. Suppression of UCH would inhibit proteasome-mediated proteolysis, a key feature of senescence.
