TRANSCRIPTIONAL ACTIVATION AND REPRESSION, 2 PROPERTIES OF THE LYMPHOID-SPECIFIC TRANSCRIPTION FACTOR OCT-2A

The lymphoid-specific transcription factor Oct-2a contains two transcr iptional activation domains which are located within the N-terminal an d C-terminal regions. To study their differential activation propertie s, we linked the isolated effector domains to the GAL4 DNA-binding dom ain. We have shown that both activating regions of Oct-2a, isolated fr om their natural context, can activate transcription as promoter facto rs. In contrast to the C-terminus, activation by the N-terminal domain is dependent on a yet unidentified factor(s) binding to the simian vi rus 40 enhancer. The results obtained by duplication of activation dom ains or their mixed combination suggest that the domains are functiona lly independent. However, activation from a remote position could only be achieved with the C-terminus of Oct-2a in B cells. In lymphoid cel ls, higher activation levels were observed, suggesting that distinct B -cell-specific cofactors in concert with the effector domains of Oct-2 a might be involved in mediating transcription from proximal and remot e positions. Furthermore, we identified a repression domain at the N-t erminus of Oct-2a. When transferred to a potent activator, transcripti onal stimulation was inhibited efficiently. These results underscore t he modular structure of Oct-2a with separable domains for activation a nd repression and suggest that Oct-2a might have complex regulatory fu nctions in vivo.