It was previously thought that it was the relatively small RNA polymerase that moves along the comparatively larger DNA template during transcription. However, increasing evidence supports the notion that due to the tethering of a transcription factory to the nuclear matrix, it is in fact the large DNA template that is moved to accommodate RNA polymerisation. In vitro studies for example have shown that RNA polymerases attached to a surface are capable of both rotating the DNA template and threading it through the polymerase to start transcription; which indicates the capabilities of RNA polymerase to be a molecular motor. Chromosome Conformation Capture (3C) also supports the idea of the DNA template diffusing towards a stationary RNA polymerase.
There remains a doubt to this mechanism of transcription. Firstly, it is unknown how a stationary polymerase is capable of transcribing genes on the (+)-strand and (-)-strand at the same genomic locus at the same time. This is in addition to a lack of conclusive evidence on how the polymerase remains immobilised (how it is tethered) and what structure it is tethered to.