C-terminal domain of LMP1 is required for its repressive activity.

(A) Diagram of wild-type and mutant LMP1 proteins. The 386-amino acid wild-type LMP1 consists of 3 major regions: a 24-amino acid cytoplasmic N-terminus (■), a transmembrane region (▩), and a 200-amino acid cytoplasmic carboxyl-terminal region. The carboxyl-terminal region can be further divided into 3 CTAR regions (). All the LMP1 point and deletion mutants are described in “Results” in detail. (B) Inhibition of CD99 promoter activity by C-terminal domain of LMP1. Various LMP1 mutants were cotransfected with p(−317/+123)luc to identify the region essential for its inhibitory function. A negative control vector pcDNA3-1-PML, a wild-type pcDNA3-LMP1, pLMP1Δ187-351, pLMP1Δ231-386, and pLMP1Δ187-386, and pAAAG are shown as control, wild-type, Δ187-351, Δ232-386, and Δ187-386 on the x-axis of the graph, respectively. The bar graph is expressed as the relative luciferase activity that is total luciferase activity divided by control transfection after the normalization with CAT activities from cotransfected pBip670CAT. Relative luciferase activity values represent mean ± SD from 3 separate transfections performed with each construct, whereas CAT values are the averages of 2 transfections among them.