Pet127 Governs a 5′ → 3′-Exonuclease Important in Maturation of Apocytochrome b mRNA in Saccharomyces cerevisiae

• Published in: The Journal of biological chemistry 2008-02, Vol.283 (7), p.3767-3772
• Main Authors: Fekete, Zsuzsanna, Ellis, Timothy P., Schonauer, Melissa S., Dieckmann, Carol L.
• Format: Article
• Language: English
• Subjects: Base Sequence; Cytochromes b - genetics; DNA Primers; Exonucleases - metabolism; Mitochondrial Proteins; RNA, Messenger - genetics; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae Proteins - physiology; Trans-Activators - physiology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M709617200

The details of mRNA maturation in Saccharomyces mitochondria are not well understood. All seven mRNAs are transcribed as part of multigenic units. The mRNAs are processed at a common 3′-dodecamer sequence, but the 5′-ends have seven different sequences. To investigate whether apocytochrome b (COB) mRNA is processed at the 5′-end from a longer precursor by an endonuclease or an exonuclease, a 64-nucleotide sequence, which is required for the protection of COB mRNA by the Cbp1 protein and is found at the 5′-end of the processed COB mRNA, was duplicated in tandem. The wild-type 64-nucleotide element functioned in either the upstream or downstream position when paired with a mutant element. In the tandem wild-type strain, the 5′-end of the mRNA was at the 5′-end of the upstream unit, demonstrating that the mRNA is processed by an exonuclease. Accumulation of precursor COB RNA in single and double element strains with a deletion of PET127 demonstrated that the encoded protein governs the 5′-exonuclease responsible for processing the precursor to the mature form.