Additionally, insertion into a gene's promoter region can have equally drastic effects. Likewise, if the viral DNA is inserted into a repressor, the promoter's corresponding gene may be over-expressed – leading to an overabundance of its product and altered cellular activity.
Adding genetic material to a gene's promoter area can lead to similar dramatic effects.  Similarly, if viral DNA is placed within a repressor, the associated gene's production might increase significantly, leading to excessive amounts of its product and changes in cell activity.