How our genome’s foes became its helpers Michael Gross  Current Biology  Volume 27, Issue 10, Pages R365-R368 (May 2017) DOI: 10.1016/j.cub.2017.04.040 Copyright © 2017 Terms and Conditions

Shared ancestry: The large family of KRAB zinc finger transcription factors goes back to a defence mechanism that originated in a common ancestor of humans and coelacanth (Latimeria chalumnae). (Photo: Mordecai 1998, CC BY-SA 4.0.) Current Biology 2017 27, R365-R368DOI: (10.1016/j.cub.2017.04.040) Copyright © 2017 Terms and Conditions

Viral threat: Retroviruses like HIV, which causes AIDS, can insert DNA transcripts of their RNA into the host genome. KRAB zinc finger transcription factors are believed to have evolved to control foreign DNA that resulted from retroviral invasions and became heritable. (Image: Hans-Ulrich Osterwalder/Science Photo Library.) Current Biology 2017 27, R365-R368DOI: (10.1016/j.cub.2017.04.040) Copyright © 2017 Terms and Conditions

Mice and men: Like humans, mice have several hundreds of KRAB zinc finger transcription factors. Compared to ours, however, those in mice point to more recent retroviral threats. (Photo: Rama/Creative Commons Attribution-Share Alike 2.0 license.) Current Biology 2017 27, R365-R368DOI: (10.1016/j.cub.2017.04.040) Copyright © 2017 Terms and Conditions

Wrapped around: Proteins with several zinc finger domains in a well-defined orientation can detect and bind specific DNA sequences. (Image: Nwkimberley/CC BY-SA 3.0.) Current Biology 2017 27, R365-R368DOI: (10.1016/j.cub.2017.04.040) Copyright © 2017 Terms and Conditions