Replication and Transcription of Mammalian Mitochondrial Dna

Abstract

Mitochondria are subcellular organelles, devoted mainly to energy production in the form of ATP, that contain their own genetic system. Mitochondrial DNA codifies a small, but essential number of polypeptides of the oxidative phosphorylation system. The mammalian mitochondrial genome is an example of extreme economy showing a compact gene organization. The coding sequences for two ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs) and 13 polypeptides are contiguous and without introns. The tRNAs are regularly interspersed between the rRNA and protein‐coding genes, playing a crucial role in RNA maturation from the polycistronic transcripts. A single major non‐coding region, called the D‐loop region, contains the main regulatory sequences for transcription and replication initiation. This genetic organization has its precise correspondence in the mode of expression and distinctive structural features of the RNAs. The basic mechanisms of mitochondrial DNA transcription and replication and the main cis‐acting elements playing a role in both processes have been determined. Many trans‐acting factors involved in mitochondrial gene expression, including the RNA and DNA polymerases, have been cloned or identified. However, the regulatory mechanisms participating in mitochondrial gene expression are still poorly understood. The interest to complete this knowledge is increased by the involvement of mitochondria in human diseases, in basic processes such as heat production, Ca2+ homeostasis and apoptosis, and by their potential role in ageing and carcinogenesis.

The complete mitogenome of the wood-feeding cockroachCryptocercus kyebangensis(Blattodea: Cryptocercidae) and phylogenetic relations among cockroach families

“…Some compact and overlapping regions were found among PCGs of animal mitogenomes (Fernandez-Silva et al 2003). We also observed a 7-bp overlap between ATP8 and ATP6, a single-base pair overlap between ATP6 and COX3, and a 7-bp overlap between ND and ND4L (Table 1).…”

A large-scale screening of the normalized mammalian mitochondrial gene expression profiles

“…A non-coding mitochondrial control region contains the main regulatory sequences for transcription and replication initiation, including a triplestranded D-loop. Though the great majority of mitochondrial proteins are encoded by the nuclear genome, mtDNA encodes 13 proteins involved in oxidative phosphorylation (for review see Hiendleder &Wolf, 2003 andFernandez-Silva et al, 2003). Individual mammalian mitochondrial-genome-encoded genes have demonstrated a number of other important biological functions, such as serving as histocompatibility antigens for the NADH dehydrogenase 1 (mt-Nd1) and cytochrome c oxidase subunit I (mt-Co1)-derived peptides (Loveland et al, 1990 ;Morse et al, 1996) or playing a role in protein folding for 12S and 16S ribosomal RNA (mt-Rnr1 and -Rnr2 ; Sulijoadikusumo et al, 2001).…”

“…Mitochondria carry out a variety of metabolic processes, their major functions being to supply the cell with energy generated by oxidative phosphorylation (OXPHOS) and to participate in protein synthesis (Fernandez-Silva et al, 2003). Both parts of mammalian genomes : nuclear DNA (nDNA) and maternally inherited mitochondrial DNA (mtDNA) are involved in OXPHOS (Enriquez et al, 1999).…”

Genetic aspects of mitochondrial genome evolution

“…A second non-coding region of only ∼30nt located inside a tRNA cluster harbours the origin of replication for the L-strand in vertebrates (Fernández-Silva et al, 2003). Arthropods, and possibly also nematodes, have a single large AT-rich non-coding region which contains the replication origins for both strands (Zhang and Hewitt, 1997;Saito et al, 2005).…”