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The “endo-symbiotic theory of mitochondrial evolution” states that mitochondrial organelles evolved from engulfed aerobic bacteria, after millions of years of symbiosis and adaptation. Here, we have exploited this premise to design new antibiotics and novel anti-cancer therapies, using a convergent approach. First, virtual high-throughput screening (vHTS) and computational chemistry were used to identify novel compounds binding to the 3D structure of the mammalian mitochondrial ribosome. The resulting library of ∼880 compounds was then subjected to phenotypic drug screening on human cancer cells, to identify which compounds functionally induce ATP-depletion, which is characteristic of mitochondrial inhibition. Notably, the top ten “hit” compounds define four new classes of mitochondrial inhibitors. Next, we further validated that these novel mitochondrial inhibitors metabolically target mitochondrial respiration in cancer cells and effectively inhibit the propagation of cancer stem-like cells in vitro. Finally, we show that these mitochondrial inhibitors possess broad-spectrum antibiotic activity, preventing the growth of both gram-positive and gram-negative bacteria, as well as C. albicans - a pathogenic yeast. Remarkably, these novel antibiotics also were effective against methicillin-resistant Staphylococcus aureus (MRSA). Thus, this simple, yet systematic, approach to the discovery of mitochondrial ribosome inhibitors could provide a plethora of anti-microbials and anti-cancer therapies, to target drug-resistance that is characteristic of both i) tumor recurrence and ii) infectious disease. In summary, we have successfully used vHTS combined with phenotypic drug screening of human cancer cells to identify several new classes of broad-spectrum antibiotics that target both bacteria and pathogenic yeast. We propose the new term “mitoriboscins” to describe these novel mitochondrial-related antibiotics. Thus far, we have identified four different classes of mitoriboscins, such as: 1) mitoribocyclines, 2) mitoribomycins, 3) mitoribosporins and 4) mitoribofloxins. However, we broadly define mitoriboscins as any small molecule(s) or peptide(s) that bind to the mitoribosome (large or small subunits) and, as a consequence, inhibit mitochondrial function, i.e., mitoribosome inhibitors.

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Exposure to GBV-C can commence at an early age, although ongoing exposure may also occur among adults with no apparent risk factors. GBV-C RNA positivity was not associated with abnormal plasma alanine aminotransferase levels among blood donors.

We explored the properties of corallopyronin A (CorA), a poorly characterized inhibitor of bacterial RNA polymerase (RNAP). It displayed a 50% inhibitory concentration of 0.73 M against RNAP, compared with 11.5 nM for rifampin. The antibacterial activity of CorA was also inferior to rifampin, and resistant mutants of Staphylococcus aureus were easily selected. The mutations conferring resistance resided in the rpoB and rpoC subunits of RNAP. We conclude that CorA is not a promising antibacterial drug candidate.

A full-length complementary DNA (cDNA) clone of the hepatitis C virus (HCV) genome was used to prepare fulllength plus-and minus-strand RNA. The minus-strand RNA, which contains a polyA ؉ tract complementary to the polyU tract found in the plus strand (genomic) RNA, but not the plus strand RNA, was captured with a commercial polyA ؉ -tract isolation system. After elution, the minus strand was amplified by reverse-transcription polymerase chain reaction (RT-PCR). The combination of this procedure and RT-PCR using rTth resulted in an unprecedented level of discrimination of 10 logs 10 . HCV minus-strand RNA isolation was unaffected by the addition of an excess of 10 4 of plus strands or by the addition of cellular RNA, and although the polyA ؉ isolation step removed 99.99% of plus strands, there was no loss of minus-strand signal. It is now apparent that approximately 80% of individuals who are infected with hepatitis C virus (HCV) develop persistent infection. The mechanism for persistence is still unclear and may be multifactorial, but one contributing factor is likely to be the low level of virus replication. As a result, viral RNA in the blood or infected tissues can only be detected by the reverse-transcription polymerase chain reaction (RT-PCR) or an equally sensitive nucleic-acid detection method. Although HCV has 6 genotypes, a number of subtypes and a quasispecies distribution in individual patients, the 5Јuntranslated region (5ЈUTR) in the genome is most highly conserved 1 and represents the most suitable (and common) target for RT-PCR. However, the core gene region is also highly conserved, and this represents an alternative suitable target. The 5ЈUTR is upstream of a single long open reading frame, which is followed by a 3ЈUTR; this is comprised of 3 elements: (1) a short 20 to 40 nt variable region immediately downstream of the stop codon in the long open reading frame (2), a poly (U) tract/polypyrimidine tract, and (3) a highly conserved 98 nt region at the extreme 3Јend. 2 It is predicted that the 5Ј and 3ЈUTRs are required for virus replication, although there are few data to confirm this, other than the finding that the 98 nt region is required for infectivity in chimpanzees. 3 HCV is classified in the Flaviviridae family and, as with other members of this family, replication is expected to be preceded by the production of a minus strand, which then forms a double-stranded RNA replicative form (RF) with the input plus strand RNA. 4 The RF then acts as the template for the synthesis of nascent plus strands. Consequently, the detection of minus-strand HCV RNA is necessary to prove virus replication in different tissues or cells, because the detection of plus-strand (genomic) RNA merely implies contamination by circulating virions. However, the detection of the HCV RNA minus strand by a strand-specific RT-PCR has proved to be more complex than simply performing a conventional RT-PCR in which an antisense primer is substituted with a sense primer in the RT step, and two studies have highlighted the di...