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This Week in PNAS: Mar 18, 2014

In the early, online edition of the Proceedings of the National Academy of Sciences, an international team led by investigators in Australia presents evidence suggesting that the arrival of humans to New Zealand hastened the disappearance of a group of large, flightless birds known as moa. For their analysis, the researchers genotyped hundreds of moa belonging to four species using remains stretching back almost 13,000 years in some cases. Data at the mitochondrial DNA and moa microsatellite markers they targeted indicated that these moa species were genetically stable prior to Polynesian settlement in New Zealand, followed by a rapid decline in the birds' numbers. "Our analyses show that moa populations were large and viable prior to human arrival in New Zealand," the study's authors write, "and their demise therefore represents a striking example of human over-exploitation of megafauna."

An American team took a look at the roots of drug resistance in Klebsiella pneumoniae isolates from the multilocus sequence type 258, which have been linked to fatal hospital acquired infections in the US and elsewhere. The isolates are often multi-drug resistant and are particularly noted for their role in carbapenem-resistant Enterobacteriaceae infections. By sequencing the reference genomes of two clinical isolates of K. pneumoniae ST258 and re-sequencing another 83 isolates from around the world, the researchers explored the genetic diversity and relationships of the ST258 isolates. A phylogenetic analysis of the isolates pointed to two ST258 clades, arguing against the notion that the sequence type can be traced back to a single clone.

Rutgers University researchers report on a system of chromatin marks and related proteins mediating the expression of heat shock protein-coding sequences and other highly expressed genes in the fruit fly. Using a Drosophila strain with an inducible hsp70 heat shock loci, the group focused on the proteins at play when histone H3 lysine 4 trimethyl and acetylated H2A marks become enriched in the promoters of highly expressed genes. Findings from a series of experiments in this system highlighted the interactions between histone H3 lysine 4 trimethyl marks, other histones, and proteins in the chromatin remodeling complex dTip60 and the dSet1 protein complex that enhance activity of genes at hsp70 loci.