FIG.1.

Expression of an antisense TBP suppresses Ras transforming function. (A) Enhanced expression of TBP mRNA by oncogenic Ras is inhibited by the expression of antisense TBP. NIH 3T3 cells were cotransfected with 500 ng of HA-tagged constitutively activated human RasV12 (pDCR-RasV12) together with 8 μg of mouse TBP antisense (AS) or sense (S) expression plasmid or vector. TBP and actin levels were determined by RT-PCR (top) and immunoblot analysis (bottom). (B) Focus-forming activity of oncogenic Ras when coexpressed with TBP antisense expression plasmid. NIH 3T3 cells were transfected as described above. For each assay, a portion of the cells were selected with 400 μg of G418 per ml, beginning 24 h posttransfection. After 18 days, cells were fixed and then treated with Giemsa stain to highlight foci and count G418-resistant colonies (10). (C) The expression of oncogenic Ras is unchanged by altering TBP expression. NIH 3T3 cells were transiently transfected as described above with vector only or with pDCR-RasV12 with or without 8 μg of AS or S expression plasmid. Cell lysates (100 μg of protein) were subjected to immunoblot analysis with HA antibody. The CRM bands represent nonspecific, cross-reacting material in the lysates.