Biochemistry, Department of


Date of this Version



The Journal of Biological Chemistry, VOL. 286, NO. 12, pp. 10137–10146, March 25, 2011


© 2011 by The American Society for Biochemistry and Molecular Biology, Inc.


Saccharomyces cerevisiae cells lacking Mne1 are deficient in

intron splicing in the gene encoding the Cox1 subunit of cytochrome

oxidase but contain wild-type levels of the bc1 complex.

Thus, Mne1 has no role in splicing of COB introns or expression

of the COB gene. Northern experiments suggest that splicing of

the COX1 aI5β intron is dependent on Mne1 in addition to the

previously known Mrs1, Mss116, Pet54, and Suv3 factors. Processing

of the aI5_ intron is similarly impaired in mne1∆ and

mrs1∆ cells and overexpression of Mrs1 partially restores the

respiratory function of mne1∆ cells. Mrs1 is known to function

in the initial transesterification reaction of splicing. Mne1 is a

mitochondrial matrix protein loosely associated with the inner

membrane and is found in a high mass ribonucleoprotein complex

specifically associated with the COX1 mRNA even within

an intronless strain. Mne1 does not appear to have a secondary

function in COX1 processing or translation, because disruption

of MNE1 in cells containing intronless mtDNA does not lead to

a respiratory growth defect. Thus, the primary defect in mne1

cells is splicing of the aI5β intron in COX1.