Actin and myosin as transcription factors.

The proteins actin and myosin have a firm place in the muscles, where they are responsible for contraction. Although recent investigations have shown that they are found in the nucleus, it has been unclear as to what they are doing there. The discovery of actin as a component of the transcription apparatus, chromatin-remodeling complexes, as well as RNA processing machines, implies important roles for actin in the readout of genetic information. Actin is associated with all three nuclear RNA polymerases and acts in concert with nuclear myosin 1 (NM1) to drive transcription. Actin-NMI interactions are involved in the transition of the initiation complex into the elongation complex, presumably by triggering a structural change of the transcription apparatus or by generating force that supports RNA polymerase movement.