Objectives: 

To examine the interaction of the HIV Tat protein and the inhibitory domain of the cellular transcription factor Oct-2.

Design: 

HIV reporter plasmids were co-transfected with expression vectors encoding wild-type and mutant Tat proteins and vectors encoding the inhibitory domain either alone or linked to a DNA-binding domain.

Methods: 

The activity of the different reporters was compared in the presence or absence of Tat or the inhibitory domain, or both.

Results: 

In the presence of the Tat protein, the Oct-2 inhibitory domain enhances the activation of Tat-responsive promoters by Tat. This effect is not observed when either the inhibitory domain or Tat cannot bind to the target gene, but is observed when one or both of the factors can bind. No activation is observed when the Oct-2 domain is co-transfected with Tat mutants that lack the Tat activation domain, indicating that the Oct-2 domain cannot substitute for the Tat activation domain.

Conclusion: 

These data indicate that the Oct-2 inhibitory domain can functionally interact with Tat to form a complex with enhanced transactivating ability.