Run-on assays showing equal transcriptional activity ofβAPr-Bcl-2 and βAPr-Ig constructs in stable transfectants of a mouse B-cell line. Nascent, labeled RNA extracted from S194 cell lines transfected with βAPr-Bcl-2, βAPr-Ig,or only the RSVneo vector was hybridized to DNA probes detecting the human β-actin RNA produced by the Bcl-2 and Ig constructs (upper row), the RSVneo RNA produced by all three cell lines transfected with the neomycine resistance gene (middle row), and the mouse histone H4 gene integral to the S194 cell line (lower row). The 145-nt β-actin fragment (p240.1) is specific for the βAPr-constructs and is therefore only seen in lanes 1 and 2.