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.
Inserting genetic material into a gene's promoter region or placing viral DNA into a repressor can both result in significant alterations to gene expression, potentially causing an overabundance of the corresponding protein and altering cellular function.