Researchers at Harvard Medical School present evidence that circadian clock negative feedback includes direct control of transcriptional termination. More specifically, they show in a Science paper published online in advance this week that "mouse PER complexes [include] RNA helicases DDX5 and DHX9, active RNA Polymerase II large subunit, Per and Cry pre-mRNAs, and SETX, a helicase that promotes transcriptional termination." During circadian clock negative feedback, RNA Polymerase II accumulates near the termination sites on Per and Cry, but not on control genes, the Harvard group says. "Recruitment of PER complexes to the elongating polymerase at Per and Cry termination sites [inhibits] SETX action, impeding RNA Polymerase II release and thereby repressing transcriptional re-initiation," it adds.
In another paper published online in advance this week, Henry Bourne from the University of California, San Francisco, and Wake Forest University School of Medicine's Mark Lively say that "unless it changes course," the US biomedical research enterprise is doomed to fail:
Over in this week's issue, Ferran Casals and Jaume Bertranpetit from the Universitat Pompeu Fabra in Barcelona, Spain, discuss two recent papers, both of which showed that most genetic variants occur at very low frequencies in human populations, and that they have accumulated an excess of potentially harmful mutations. "The development of agriculture and livestock in the transition from the Paleolithic to the Neolithic era some 10,000 years ago heralded a demographic explosion in our species that is still ongoing today," Casals and Bertranpetit say. "Paradoxically, this rapid population growth, made possible by improved living conditions, may be responsible for an excess of damaging variants in our genome."
Also in this week's Science, investigators at Michigan State University and Harvard Medical School show that "a single promoter inversion switches Photorhabdus between pathogenic and mutualistic states."