Mechamism of non-AUG initiation in yeast ALA1

• Main Authors: Chan-Hsien Yeh, 葉蟬嫻
• Other Authors: Chien-Chia Wang
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/55177969592845409939

碩士 === 國立中央大學 === 生命科學研究所 === 91 === It was recently shown that ALA1, the only gene in Saccharomyces cerevisiae coding for alanyl-tRNA synthetase (AlaRS), encodes both cytoplasmic and mitochondrial forms. The former is translationally initiated at the ATG codon (designated ATG1) at the 5’-end of its open reading frame, while the latter is initiated from upstream in-frame redundant non-ATG codons (i.e., ACG-25 and ACG-24). In this thesis, I investigated the translational mechanism of ALA1 by which long and short protein isoforms were produced from the single gene. Like many known non-ATG initiators, a secondary structure is identified downstream of ACG-25. However, mutations that destroy the secondary structure do not impair its initiating activity. Functional tests, in combination with Western blot analysis, suggest that the isoforms of AlaRS can be translated from long and short transcripts by alternative transcription/translation, or from a single transcript by leaky scanning. To our knowledge, this appears to be a novel case where both leaky scanning and alternative transcription/translation are involved in the production of protein isoforms.