GENE impedance: a natural process for control of gene expression and the origin of RNA interference.

Gene expression is controlled by coordinated transcriptional and post-transcriptional mechanisms. Normally, expression of a gene switches on and off in response to specific physiological signals that are triggered by cellular demand for the gene products at a given time. Based on our previous studies and the scientific literature, we hypothesize that when a gene promoter switches to transcriptional repression mode, transcription of the gene ceases, and a small amount of double-stranded RNA (dsRNA) is synthesized by the RNA polymerase switching to the opposite DNA strand at the termination region of the gene. These dsRNA structures, which result from normal transcriptional repression, can then be processed into short interfering RNAs (siRNAs) within the nucleus. These molecules subsequently direct specific cleavage of the cognate mRNAs and interfere with their translation through sequence complementarily. We further hypothesize that cellular defense mechanisms invoked by invading genetic elements could be rooted in this fundamental regulatory pathway that we call "GENE impedance", or simply, GENEi. Here, we present a working model that illustrates how transcription-termination and transcription-arrest can contribute to the regulation of gene expression via GENEi. In our model RNAi is only one component of GENEi, which is a more generalized mechanism of gene regulation.