NPM/B23 protein expression is downregulated in Jurkat cells stably expressing HIV-1 TAR. A) Two-dimensional gel electrophoresis [isoelectric point (pI) range: 4 to 6.7] comparing clones of stable Jurkat cell lines expressing U6-TAR (TAR-3) or U6-shNEG (NEG-1). B) A region of the panel in A) is enlarged to show spots of the downregulated NPM/B23 protein in TAR-3 cell line (bottom left panel) compared to the control NEG-1 cell line (upper right panel). The six (6) spots identified as NPM/B23 (see results for details) are circled (TAR-3 panel). C) Proteomic analysis of the spots identified in B) showed there was a 1.5 to 3-fold decrease in the expression of the NPM/B23 protein in the Jurkat TAR-3 cell line, compared to Jurkat NEG-1 cells.