Abstract
Expression of CGS1 is down-regulated at the step of mRNA degradation in response to S-adenosylmethionine. A fourteen amino acid sequence, termed the MTO1 region, encoded within CGS1 exon 1 is responsible for this regulation. Translation arrest was observed prior to mRNA degradation in a cell-free system of wheat germ extract. This arrest occurs at the position where the ribosomal A site resides at the Ser-94 codon. The Trp-93 and Ser-94 residues are located downstream of the MTO1 region and are widely conserved in higher plants. Substitution of Ser-94 with other amino acids confirmed that Ser-94 is important for the efficiency of the translation arrest and for determining the translation arrest position. We next examined the importance the distance between the MTO1 region and the Trp-93/Ser-94 residues. Changes in the translation arrest response suggested that this distance is also important for CGS1 regulation.
