FIG. 1.

The HTLV-1 p12^I protein binds to the free MHC-I-Hc but not to the MHC-I-Hc–β₂-microglobulin complex. Radioimmunoprecipitation was performed on lysates of transfected HeLa-Tat cells with αHA1, PT85A, or isotype-matched IgG antibodies. Lysates were analyzed on 10% (A) and 15% (B) acrylamide gels. Arrows indicate the expression of p12^IK88 (lanes 1 and 2) and MHC-I-Hc and β₂-microglobulin (lanes 5 and 6) and the coimmunoprecipitation of free MHC I-Hc and p12^IK88 with the HA1 antibody (lane 2). Ubiquitinated forms of p12^IK88 are indicated by arrows on the left. (C) Lysates were also precipitated with an αcalnexin antibody (10% acrylamide gel).