Major transcription start site for bcl-x in human erythroblasts.

Left panel: labeled, ssDNA consisting of the noncoding strand of the sequence from −858 through −389 of the human bcl-xsequence (GenBank accession number AL160175) was hybridized to 25 μg total RNA from human erythroblasts derived by 10 days of culture of partially purified erythroid progenitors.22 Lanes 1 and 2 are duplicates showing the major protected fragments after S1 nuclease digestion. Full-length probe (not shown) was 519 nucleotides long. The leftmost lanes of the panel contain labeled sequencing reactions from a portion of the human coagulation Factor XI gene, as in Figure 2A. Right panel is a reproduction of Figure 2A.