Inactivated or unusual DGRs. We encountered several examples of DGRs with inactivated RTs, but intact VR/TR repeats. This includes (A) nonsense mutations as in Ruminococcus gnavus ATCC 29149, where a premature stop codon truncates the RT ORF, (B) disruption of the RT ORF by insertion elements as in Acaryochloris marina MBIC11017, or (C) frameshift mutations as in Bacteroides sp. 9_1_42FAA. (D) Some DGRs contain full-length RT ORFs, but several B-to-N mutations in their VR. VRs of the respective elements are shown on the left and depicted in yellow (A-to-B mutations: orange vertical bars; B-to-N mutations: black vertical bars). The corresponding RTs are schematically shown on the right (not to scale). The 5’ part of the RT is shown as green box, inactivated parts in gray.
Schillinger et al. BMC Genomics 2012 13:430 doi:10.1186/1471-2164-13-430