Abstract
S18 family of mitochondrial ribosomal proteins (MRPS18, S18) consists of three members, S18-1 to −3. Earlier, we found that overexpression of S18-2 protein resulted in immortalization and eventual transformation of primary rat fibroblasts. The S18-1 and −3 have not exhibited such abilities. To understand the differences in protein properties, the evolutionary history of S18 family was analyzed. The S18-3, followed by S18-1 and S18-2 emerged as a result of ancient gene duplication in the root of eukaryotic species tree, followed by two metazoan-specific gene duplications. However, the most conserved metazoan S18 homolog is the S18-1; it shares the most sequence similarity with S18 proteins of bacteria and of other eukaryotic clades. Evolutionarily conserved residues of S18 proteins were analyzed in various cancers. S18-2 is mutated at a higher rate, compared with S18-1 and −3 proteins. Moreover, the evolutionarily conserved residue, Gly132 of S18-2, shows genetic polymorphism in colon adenocarcinomas that was confirmed by direct DNA sequencing.Concluding, S18 family represents the yet unexplored important mitochondrial ribosomal proteins.
Highlights
Mitochondrial ribosomal proteins (MRPs) are encoded by nuclear genomic DNA, MRPs are important structural constituents of mitoribosome, a key component of mitochondrial translation machinery
We found that overexpression of S18-2 protein resulted in immortalization and eventual transformation of primary rat fibroblasts
The results show that the S18-1 is the most conserved metazoan homolog followed by S18-2 and S18-3
Summary
Mitochondrial ribosomal proteins (MRPs) are encoded by nuclear genomic DNA, MRPs are important structural constituents of mitoribosome, a key component of mitochondrial translation machinery. Mammalian 55S mitoribosome is composed of two parts: 28S small and 39S large subunits. During the evolution of the 55S mammalian mitoribosome, the ancestral mitoribosome (70S) underwent key structural alterations. Mammalian mitoribosome contains more proteins than the bacterial ribosome; 55S ribosomes are larger than bacterial ribosomes despite the loss of approximately half of their RNA [3]. Functions of a few MRPs have been characterized and are central to oxidative phosphorylation (OXPHOS) pathways [4]. Several MRP genes have been mapped to loci associated with disorders consistent with defective oxidative phosphorylation, such as multiple mitochondrial dysfunctions, Leigh syndrome, and nonsyndromic hearing loss [5]
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