In an advance, online publication of Nature this week, an international research team reports the complete mitochondrial DNA genome of an unknown hominin from southern Siberia. The mtDNA was retrieved from a bone excavated in 2008 in Denisova Cave in the Altai Mountains, the researchers write, and represents a "hitherto unknown type of hominin mtDNA that shares a common ancestor with anatomically modern human and Neanderthal mtDNAs about one million years ago." The researchers suggest that the Denisova hominin lived closely in time and geographical proximity with Neanderthals as well as modern humans.
An international research team presents their finding that Skp2 targeting suppresses tumorigenesis via Arf-p53-independent cellular senescence. "…Although Skp2 inactivation on its own does not induce cellular senescence, aberrant proto-oncogenic signals as well as inactivation of tumor suppressor genes do trigger a potent, tumour-suppressive senescence response in mice and cells devoid of Skp2," the authors write, adding that genetic inactivation of Skp2 elicits senescence even in oncogenic conditions in which the p19-Arf-p53 response is impaired. The team suggests that pharmacological inhibition of SKp2 represents an approach for further study of cancer prevention and therapy.
Published in advance online, new research from investigators at the National Institute on Aging and their colleagues reports that Zscan4 regulates telomere elongation and genomic stability in mouse embryonic stem cells. While only five percent of ES cells express Zscan4 at a given time, the resarchers write, nearly all ES cells activate Zscan4 at least once. The Zscan4 positive state in ES cells is associated with rapid telomere extension and the up-regulation of meiosis-specific homologous recombination genes. They also show that Zscan4 knock-down shortens telomeres, increases karyotype abnormalities, and slows down cell proliferation, among other things.
In Nature Chemical Biology, a pair of researchers from the University of Calgary in Canada reports their elucidation of two genes responsible for morphine biosynthesis in the opium poppy. Using functional genomics, the team isolated thebaine 6-O-demethylase and codeine O-demethylase, the "only known 2-oxoglutarate/Fe(II)-dependent dioxygenases that catalyze O-demethylation." Then, using a virus-induced gene silencing method, the investigators found that T6ODM and CODM efficiently blocked metabolism at thebaine and codeine, respectively. "The evolution of these two genes in a single plant species has had such a huge impact on humanity over the past several thousand years," said Peter Facchini, a co-author of the study, in a statement. "Our discovery allows this unique genetic power to be harnessed in many important ways."