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. 2007 Aug 1;81(20):10914–10923. doi: 10.1128/JVI.01208-07

FIG. 2.

FIG. 2.

Overexpression of c-Myc negatively regulates HIV-1 LTR transcription. (A) c-Myc blunts Tat-activated LTR expression in HeLa-CAT-CD4 cells. pCMV vector, pCMV-Tat, pGCN-c-Myc, or pGCN-c-Myc plus pCMV-Tat were transfected into HeLa-CAT-CD4 cells. CAT reporter gene expression was assayed by real-time PCR after 48 h. RNA PCR demonstrates that GAPDH (loading control) and transfected Tat expression levels are equivalently unaffected by c-Myc. Relative CAT reporter gene expression was normalized to a value of 1.0 for pCMV-transfected cells. Bars indicate standard errors of the means for three independent experiments. P values are given for comparisons with vector control. n.s., not significant. (B) Dose-dependent inhibition of Tat activation by c-Myc. LTR expression was monitored in the presence of increased ratios of pGCN-c-Myc to pCMV-Tat (1:1, 1:2, 1:3, and 1:4). At the highest dose of c-Myc vector, Tat activation was repressed 5.7-fold (P < 0.001).