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Abstract Detail


Mechanisms of Gene Regulation

Choi, Yu Jin [1], Park, Ky Young [1].

Translational regulation of the plant S-adenosylmethionine decarboxylase by a sequence-dependent upstream open reading frame by phosphorylation.

S-adenosylmethionine decarboxylase (SAMDC; EC 4.1.4.50) is a key enzyme in the biosynthesis of the polyamines spermidine and spermine. Carnation SAMDC (CSDC9) mRNA 5¸-leader sequences contain two highly conserved overlapping 5¸ tiny and 3¸ small uORFs. We have provided the direct evidence of peptide synthesis from the small uORF in SDS-PAGE using a wheat germ in vitro transcription/translation system. To investigate the function of the uORFs, several point-mutated genes with the β-glucuronidase (GUS) coding sequence under the control of 35S promoter were constructed. When we measured GUS transcripts and enzyme activity in various transgenic tobacco plants, downstream GUS translational efficiency were inhibited by small uORF in sequence-dependent manner. Also, we showed that the uORF protein specifically was phosphorylated by unknown kinase in cell-free system. Putative phosphorylation sites for protein kinase C, cAMP and cGMP dependent kinase and casein kinase Ⅱ in uORF peptide might be important for inhibitory effect of uORF. To test whether the phosphorylated uORF protein was functional, several phosphorylation site-mutated constructs consisting of the GUS coding sequence under the control of the 35S promoter were constructed. Changes in phosphorylated uORF expression pattern and phenotypes of transgenic plants had been observed in this study. Various transgenic tobacco plants with eliminating specific phosphorylation sites showed that translational efficiency was changed of downstream GUS. This is the first report to provide evidence that phosphorylation of small uORF may repress the translation of downstream ORF in sequence-dependent manner in plant mRNAs. We will discuss the mechanism of post-transcriptional control of uORF by phosphorylation.


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1 - Sunchon National University, Biology, 315 Maegok, Sunchon, Chonnam, 540 742, Korea

Keywords:
S-adenosylmethionine decarboxylase
Upstream open reading frame
gene regulation
Phosphorylation.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P36009
Abstract ID:408


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