Figure 7.

Transcription start site mapping. (A) RT-PCR with cDNA from IN157 cells. Only BF42 and BF8 generate a specific product, hybridizing with BR4. The sequences and annealing conditions of all primers are correct, however, as products of expected sizes are amplified from genomic DNA. The transcription start, therefore, is between the sequences corresponding to BF15 and BF42. (B) Primer extension analysis of mouse heart RNA indicates a single transcription start on the C residue at mouse position 1183. (C) The region around the transcription start is homologous to the initiators of other promoters. Consensus 1, initiator consensus derived from sequence comparison of Inr⁺ genes (32); consensus 2, experimentally derived consensus for functional initiator (33); TdT, terminal deoxynucleotidyl transferase; hRAR, human retinoic acid receptor α; mCREB, mouse cAMP response element binding protein. Transcribed sequence is indicated in bold uppercase.