 However, in recent gene therapy techniques, retroviruses are often used to deliver desired genes instead of their own viral genome into the host genome.As such, we are interested in the host cell's mechanisms to silence such gene expressions to find out firstly, how the host cell manages provirus transcription to eliminate the deleterious effects of retroviruses; and secondly, how can we ensure stable and long term expression of retrovirus-mediated gene transfer.It has been found that the level transcription of integrated retroviruses depends on both genetic and chromatin remodeling at the site of integration.