Different approaches to encode additional proteins in the HIV-1 genome were tested.
IRES translation elements are incompatible with efficient HIV-1 replication.
Ubiquitin and 2A fusion protein approaches allow efficient HIV-1 replication.
Doxycycline-controlled HIV-1 variants that encode all viral proteins were developed.
Nef stimulates HIV-rtTA replication in primary cells and human immune system mice.