| Popis: |
Many ribosome binding and translation initiation signals are located in the 5’ untranslated regions (UTR) of messenger RNAs (mRNA). Noncanonical mRNA can reveal novel mechanisms by which initiation may be regulated based on mRNA primary sequence. We used Escherichia coli mRNAs containing multiple start codons to study how one open reading frame (ORF) can impact the expression of another and how ribosomes discriminate initiator sites during start site selection. In chapter 1 we studied the effects of a 5’ terminal AUG and its ORF on the downstream SD-led CDS. In chapter 2 we used the aroL gene, which contains multiple AUG triplets within the 5’ UTR, to study start site selection between two initiator codons divided by only two nucleotides. We used ß-galactosidase assays to assess protein expression from lacZ fusions and toeprint assays to determine ribosome binding patterns. We found there are a myriad of signal features by which the mRNA sequence can regulate expression from a start site. Furthermore, all the mRNA transcripts studied here use unique mechanisms to control this initiation regulation. |
