Expression vectors are disclosed that are comprised of (a) one or more
silencer elements and conditionally inducible elements to form silencer-inducible
regions and (b) promoters in operative linkage upstream of at least one expressed
region. The expression vector thereby regulates expression of at least one downstream
region by conditional silencing in which an expressed DNA region of a gene is transcribed
to produce RNA transcripts, which may or may not be translated to produce polypeptides.
Genetically engineered mammalian cells and non-human mammals can be made using
such expression vectors through transfection and transgenesis techniques. Moreover,
processes of making and using the aforementioned products are disclosed (e.g.,
the expression vector may be used diagnostically, therapeutically, or prophylactically).
