Efficiency of a non-AUG initiator is drastically affected by its sequence context in yeast

• Main Authors: Shun-Jia Chen, 陳順佳
• Other Authors: 王健家
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/79710603324992341940

碩士 === 國立中央大學 === 生命科學研究所 === 95 === Previous studies have shown that translation of the yeast GRS1 gene is alternatively initiated from a UUG and a downstream AUG triplet. Evidence presented here shows that recognition of these two initiators is mainly mediated by a mechanism known as leaky scanning. Unlike an AUG initiator, efficiency of the non-AUG initiator is drastically affected by its flanking sequences. In particular, the nucleotides at its relative positions -1, -2, and -3. A/A/X (X represents A or G) and C/G/C appear to be the most and least favorable sequences at these positions, respectively. Mutation of the native context sequences -3 ~ -1 from AAA to CGC reduces the initiating activity of the UUG initiator up to 32-fold and results in loss of mitochondrial activity. While an AUG initiator is in general unresponsive to context changes, an AAA(-3 ~ -1) to CGC mutation still reduces its initiating activity up to 8-fold under similar conditions. These results suggest that sequence context is more important than previously expected for initiation in yeast.