The differential overamplification of short sequences in the mitochondrial DNA of rho- petites in Saccharomyces cerevisiae stimulates recombination

Increased copy number of mitochondrial DNA predicts poor prognosis of esophageal squamous cell carcinoma

Change in mitochondrial DNA (mtDNA) copy number has been reported in esophageal squamous cell carcinoma (ESCC). However, its prognostic implication in ESCC remains largely unknown. Using reverse transcription-quantitative PCR assay, the mtDNA copy number was assessed in a cohort of patients with ESCC (n=141) and normal esophageal tissues (n=45), and the association between variable mtDNA levels and clinical outcomes of patients with ESCC were studied. Data revealed that ESCC patients exhibited an increased mtDNA content compared to control subjects. Furthermore, increased mtDNA content was associated with a significantly increased risk of cancer-associated mortality. This molecular event was associated with poorer survival in patients with ESCC, and was an independent predictor of patient survival. Data demonstrated that increased mtDNA content is a common genetic event in ESCC and may be a predictive factor of poor prognosis for ESCC patients.

Imported sequences in the mitochondrial yeast genome identified by nucleotide linguistics

In addition to universally appearing mitochondrial (mt) genes, origins of replication and transcription start regions typical of all mt genome variants of the yeast Saccharomyces cerevisiae, the mt genomes of some of the strains contain variable sequences. These sequences are apparently largely dispensable. They are mainly composed of group-I and -II introns and intergenic open reading frames (ORFs). Many of the introns contain ORFs, some of which were shown by genetic and biochemical means to be involved in splicing and transposition of the mt introns. Some of the optional sequences are hypothesized to be mobile genetic elements. Nucleotide (nt) sequences of the mt genome of S. cerevisiae were examined by analyzing occurrences of oligodeoxyribonucleotide (oligo) 'words'. This linguistic technique had been found to be sensitive to both function and origin of the sequence [Pietrokovski et al., J. Biomol. Struct. Dyn. 7 (1990) 1251-1268]. A clear difference is found between the oligo vocabularies of the optional and basic yeast mt sequences. The difference is mainly located in protein coding segments of the optional sequences which contain conserved amino acid motifs, characteristic of intronic and intergenic ORFs. The use of nt linguistics to detect the sequence dissimilarity and its causes in yeast mitochondria provides fast and straightforward results, identifying the intronic and intergenic ORFs as DNA sequences of foreign, non-mt origin.