Overexpression of a novel member of the mitochondrial carrier family rescues defects in both DNA and RNA metabolism in yeast mitochondria

Abstract

The PIF1 and MRS2 gene products have previously been shown to be essential for mitochondrial DNA maintenance at elevated temperatures and mitochondrial group II intron splicing, respectively, in the yeast Saccharomyces cerevisiae. A multicopy suppressor capable of rescuing the respiratory deficient phenotype associated with null alleles of either gene has been isolated. This suppressor is a nuclear gene that was called RIM2/MRS12. The RIM2/MRS12 gene encodes a predicted protein of 377 amino acids that is essential for mitochondrial DNA metabolism and proper cell growth. Inactivation of this gene causes the total loss of mitochondrial DNA and, compared to wild-type rhoo controls, a slow-growth phenotype on media containing glucose. Analysis of the RIM2/MRS12 protein sequence suggests that RIM2/MRS12 encodes a novel member of the mitochondrial carrier family. In particular, a typical triplicate structure, where each repeat consists of two putative transmembrane segments separated by a hydrophilic loop, can be deduced from amino acid sequence comparisons and the hydropathy profile of RIM2/MRS12. Antibodies directed against the aminoterminus of RIM2/MRS12 detect this protein in mitochondria. The function of the RIM2/MRS12 protein and the substrates it might transport are discussed.

Mitochondrial pyrimidine nucleotide carrier (PNC1) regulates mitochondrial biogenesis and the invasive phenotype of cancer cells

“…When PNC1 was reduced by 80% (as routinely obtained with siRNA number 2) this resulted in a reduction in mtDNA content of approximately 80%, whereas cells with PNC1 suppressed by 40-60% of PNC1 (siRNA1 and shRNA) showed a 40-60% reduction in mtDNA content (Figure 3e; unpublished data). The necessity for PNC1 in mtDNA maintenance is apparently conserved throughout evolution because deletion of the yeast homologue Rim2p causes loss of mtDNA (Van Dyck et al, 1995). Interestingly, Rim2p overexpression can also rescue mtDNA deletion observed in yeast lacking the DNA helicase PIF1.…”

The Bacterial Magnesium Transporter CorA Can Functionally Substitute for Its Putative Homologue Mrs2p in the Yeast Inner Mitochondrial Membrane

“…This notion is supported by our observations that high Mg 2ϩ concentrations in the medium enhance this suppression in vivo (not shown) and partially restore self-splicing of M1301 mutant RNA in vitro. 2 Moreover, the absence of Mrs2p is compensated for by Mrs3p, Mrs4p, or Mrs12p, three members of the mitochondrial carrier family, and we have speculated previously that they may be involved in the transport of cations (14,28).…”

A Specific Role of the Yeast Mitochondrial Carriers Mrs3/4p in Mitochondrial Iron Acquisition under Iron-limiting Conditions

“…Flx1p, FAD (13); Leu5p, coenzyme A (14)). (iii) Several genes encoding members of the MCF were identified by genetic screens that did not immediately allow any conclusions with respect to their substrates (MRS3 and MRS4 (15); MRS12/RIM2 (16); YHM1/SHM1 (17); YHM2 (18)). (iv) Limited information from systematic studies is available for a few genes encoding predicted mitochondrial carrier proteins (19,20), while (v) nothing is known about the remaining open reading frames.…”