Transcription factor binding and transactivation capacity of the E box of β₂m.

(A) EMSA showing binding of complexes to the E box of β₂m. Using specific Abs, the complex binding to the E box was shown to contain USF1 and USF2 in Jurkat, Raji, and THP-1 cells. The presence of E47 was not detected. Arrowheads indicate the USF1/USF2 complex; *, supershifted complex(es). (B) Transient transfection of wild-type β₂m- and E box–mutated reporter constructs with USF1 and USF2 expression vectors (1 μg) in Tera-2 cells. The luciferase activity values were normalized with the Renillaluciferase activity values and are expressed as mean ± SD of 4 samples. The induction ratios are indicated above the histogram. RLU indicates relative light units.