Messenger RNAs transcribed from yeast linear cytoplasmic plasmids possess unconventional 5’ and 3’ UTRs and suggest a novel mechanism of translation

Václav Vopálenský; Michal Sýkora; Tomáš Mašek; Martin Pospíšek

Tables S1A, S5). We found only two ORFs of the fifteen encoded by the pGKL plasmids, of which at least 90% of the transcripts were 5' capped. At least 50% of capped transcripts were found in mRNAs corresponding to five ORFs, which is one-third of all ORFs encoded by the pGKL plasmids (Figs. 1, 3C; Table S1A ). Non-template adenosine nucleotides were less likely added at the 5' ends of mRNAs transcribed from ORFs whose more than 50% transcripts were capped. Conversely, longer 5' poly(A) leaders were found in mRNAs transcribed from ORFs that yielded less frequently capped or completely uncapped transcripts ( Fig. 3C ; Table S1A ). However, both non-templately added adenosine nucleotides and mRNA caps were frequently found within identical transcripts (Fig. 3A) . We calculated the number of non-template adenosine nucleotides in the 5' leaders of the mRNAs of each pGKL ORF as well as the minimal number of template and non-template adenosines found at the 5' ends of their uncapped transcripts and the fractions of capped mRNAs and mRNAs containing nontemplate 5' adenosine nucleotides. We also calculated the medians and means of the numbers of non-template adenosine nucleotides added per mRNA molecule from each pGKL ORF.