FIG. 9.

Treatment with the deacetylase inhibitor trichostatin A upregulates the expression of the LMP1 gene and induces the lytic cycle in some EBV-transformed B-cell lines. Trichostatin A (TSA) was added to the culture media of three EBV-positive cell lines, Rael, P3HR-1, and Daudi, and the expression of the LMP1 and BZLF1 proteins was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting. For control purposes, the expression of LMP1 and BZLF1 was induced in parallel cultures by using 5-azacytidine (5-azaC), TPA, or n-butyrate, depending on the cell line, as indicated above the lanes and described in Materials and Methods. (A) The mouse anti-LMP1 antibody CS 1-4 was used. The positions of the full-length LMP1 and the truncated form found in lytically infected cells are indicated on the right. The sizes of the LMP1 proteins differ between the cell lines due to varying numbers of a specific repeat in the proteins. (B) The mouse anti-BZLF1 antibody was used. It should be noted that the BZLF1 protein was expressed at low levels in uninduced P3HR-1 cells. This cell line is known to contain lytic cell subpopulations. A longer exposure of the autoradiogram for the Daudi cell extracts was required in order to detect BZLF1 protein expression. Numbers on the left are molecular masses in kilodaltons.