A public-private team including investigators from SomaGenics, the University of California, San Francisco, Integrated DNA Technologies, and Stanford University School of Medicine shows in a paper published online in advance in Nucleic Acids Research this week that certain short shRNAs — or sshRNAs, which are "designated as L-type or R-type according to whether the loop is positioned 3′ or 5′ to the guide sequence, respectively" — require loop cleavage for optimum activity.