AID has been shown in vitro to be active on single-strand DNA, and has been shown to require active transcription in order to exert its deaminating activity. The involvement of Cis-regulatory factors is suspected as AID activity is several orders of magnitude higher in the immunoglobulin "variable" region than other regions of the genome that are known to be subject to AID activity. This is also true of artificial reporter constructs and transgenes that have been integrated into the genome. A recent publication suggests that high AID activity at a few non-immunoglobulin targets is achieved when transcription on opposite DNA strands converges due to super-enhancer activity.