Destabilization of Chlamydomonas chloroplast rbcL transcripts after adding 19 nucleotides to their 5` untranslated region

Abstract

The gene rbcL in the Chlamydomonas chloroplast codes for a mRNA of about 1.6 kb including a 5`UnTranslated Region (5`UTR) of 92 bp.The beginning of the 5`UTR has two stem-loops as part of its secondary structure. A 10-nucleotide element found to be crucial for transcript stability lies at the base in between these two stem-loops. Addition of nucleotides to the 5`terminus of rbcL transcripts has in some cases made the transcript unstable depending both on the number and type of nucleotides added. In this study a 19 nucleotide sequence was added to the 5`terminus of the rbcL 5`UTR in a chimeric reporter gene construct to study its effect on RNA stability.The 19 added nucleotides were not predicted to fold into any secondary structure or to influence folding of the original 5`terminus in any way. Due to the added nucleotides accumulation of transcripts was completely abolished suggesting that transcripts became susceptible to RNase attacks