Analysis of LAT transcription. Shown is an autoradiogram of a Northern blot with probes specific for ORF71 (lanes 1 and 2), ORF72 (lanes 2 and 3), and ORF73 (lanes 5 and 6) of BCBL-1 RNA from TPA-induced (lanes 2, 4, and 6) or mock-treated (lanes 1, 3, and 5) cells. The blot was rehybridized with a GAPDH probe as a loading control. The arrows indicate the migration of the 5.8- and 1.7-kb messages.