Overexpression of wild type Tat rescues the unspliced viral mRNA levels suppressed by Nullbasic in HIV-1 expressing cells. Total RNA was extracted from HEK293T cells transfected to express the HIV-1 infectious provirus, pGCH, and co-transfected at a 1:2 molar ratio with either empty vector (“No Tat”) or plasmids expressing Nullbasic-FLAG (“NB”), Tat-FLAG (“Tat”), or Nullbasic-FLAG with Tat-FLAG (“NB + Tat”). The levels of total (black columns) and unspliced (gray columns) HIV-1 mRNAs were assayed by quantitative RT-PCR using primers specific for total and unspliced viral mRNA. Results represent the means and standard deviations of triplicate assays from 3 independent experiments, with unspliced viral mRNA levels expressed relative to total viral mRNA levels. Significant differences between data were determined using Welch’s t-test against a two-tailed distribution, the p values from which are indicated.