Also accepted an explanation that the two-hybrid system allows measurement of the strength of interaction. Since I didn't catch the typo until marking the test, I gave you the benefit of the doubt on your answers. The transgene is being inserted directly into the target tissue. Indirect therapy would involve injecting transfected cells into the target tissue. Since the transgene is directly injected, there is no need for tissue-specific regulation of transcription.
Most retroviruses can replicate only in actively mitotic cells.
Since cancerous cells are rapidly dividing, retroviral vectors are most likely to reproduce there, as opposed to non-target tissues. IF1 causes the 50S and 30S subunits to disassociate. IF3 binds to 30S and prevents reassociation. The 50S subunit binds, causing the dissociation of IF1 and IF3. GTP-hydrolysis then allows dissociation of IF2.