Locations of the binding sites for C/EBP, TATA binding protein, Sp factors, NF-κB and ATF/CREB factors are shown (not to scale). Although no canonical C/EBP-binding sites have been identified within the HTLV-1 long terminal repeat, C/EBP has been shown to be able to bind to TRE-1 repeat III. The three 21 bp repeats of TRE-1 are illustrated on the HTLV-1 long terminal repeat.
ATF: Activating transcription factor; C/EBP: CCAAT/enhancer protein; CREB: cAMP response element binding protein; HTLV: Human T-cell leukemia virus type 1; NF-κB: Nuclear factor-κB; TRE: Tax-responsive element.