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This Week in PNAS: Jun 4, 2013

A group of Australian researchers previously found that Wolbachia, an insect endosymbiont, manipulates host microRNA levels so that it is maintained in Aedes aegypti, the dengue virus vector. This week, they report in the Proceedings of the National Academy of Sciences that Wolbachia represses the expression of AaDnmt2, the Ae. aegypti DNA methyltransferase gene, while the dengue virus induces its transcription. Wolbachia, they note, suppresses the methyltransferase gene through the miRNA, aae-miR-2940. Further, overexpression of AaDnmt2 leads to decreased Wolbachia replication, but increased dengue virus replication in the mosquito. "Taken together, our studies suggest that aae-miR-2940 plays an important role not only in the maintenance of Wolbachia infection in mosquito cells, but also contributes to the resistance to DENV infection in mosquito cells," the researchers write.

Using a genome-wide RNAi screen, researchers from Mexico and Boston searched for proteins involved in the rotovirus lifecycle, as they report in PNAS. In a cell culture, they uncovered more than 500 such proteins, including ones involved in the endosomal sorting complex required for transport, or ESCRT, complex. That complex, they researchers further found, appears to mediate rotovirus cell entry. "This work reports the direct involvement of the ESCRT machinery in the life cycle of a nonenveloped virus and highlights the complex mechanism that these viruses use to enter cells," the write.

Using SNP data from more than 2,000 people from 43 populations from Europe and Africa, researchers led by Stanford University's Carlos Bustamante report that the genetic diversity seen in southern European populations is due to gene flow from North African populations. In particular, southwestern Europeans showed high levels of shared ancestry with North Africans. However, southeastern Europeans had higher levels of shared ancestry with populations from the Near East than the southwestern Europeans. "The haplotype sharing we observe between Europe and the Near East follows a southeast to southwest gradient, whereas sharing between Europe and the Maghreb follows the opposite pattern; this suggests that gene flow from the Near East cannot account for the sharing with North Africa," the researchers note.

GenomeWeb Daily News has more on this study, here.