Access the full text.
Sign up today, get DeepDyve free for 14 days.
The mitochondrial genome of Chlamydomonas reinhardtii encodes eight protein coding genes transcribed on two polycistronic primary transcripts. The mRNAs are endonucleolytically cleaved from these transcripts directly upstream of their AUG start codons, creating leaderless mRNAs with 3′ untranslated regions (UTR) comprised of most or all of their downstream intergenic regions. In this report, we provide evidence that these processed linear mRNAs are circularized, which places the 3′ UTR upstream of the 5′ start codon, creating a leader sequence ex post facto. The circular mRNAs were found to be ribosome associate by polysome profiling experiments suggesting they are translated. Sequencing of the 3′–5′ junctions of the circularized mRNAs found the intra-molecular ligations occurred between fully processed 5′ ends (the start AUG) and a variable 3′ terminus. For five genes (cob, cox, nd2, nd4, and nd6), some of the 3′ ends maintained an oligonucleotide addition during ligation, and for two of them, cob and nd6, these 3′ termini were the most commonly recovered sequence. Previous reports have shown that after cleavage, three untemplated oligonucleotide additions may occur on the 3′ termini of these mRNAs—adenylation, uridylylation, or cytidylation. These results suggest oligo(U) and oligo(C) additions may be part of the maturation process since they are maintained in the circular mRNAs. Circular RNAs occur in organisms across the biological spectrum, but their purpose in some systems, such as organelles (mitochondria and chloroplasts) is unclear. We hypothesize, that in C. reinhardtii mitochondria it may create a leader sequence to facilitate translation initiation, which may negate the need for an alternative translation initiation mechanism in this system, as previously speculated. In addition, circularization may play a protective role against exonucleases, and/or increase translational productivity.
Current Genetics – Springer Journals
Published: Jun 1, 2018
Read and print from thousands of top scholarly journals.
Already have an account? Log in
Bookmark this article. You can see your Bookmarks on your DeepDyve Library.
To save an article, log in first, or sign up for a DeepDyve account if you don’t already have one.
Copy and paste the desired citation format or use the link below to download a file formatted for EndNote
Access the full text.
Sign up today, get DeepDyve free for 14 days.
All DeepDyve websites use cookies to improve your online experience. They were placed on your computer when you launched this website. You can change your cookie settings through your browser.