Transcription initiation sites in the ALCAM gene. A) Schematic diagram of the 5'RACE approach. Positions of primers AL1, AL2 and AL3 are shown. B) Ethidium bromide stained agarose gel showing DNA marker (lane 1), and products of 5'RACE reaction using primers AAP and AL2 (lane 2), UAP and AL3 (lane 3). Lane 4 is negative PCR control (BL). C) Sequence of a 5' UTR clone of ALCAM showing multiple sites of RNA synthesis (arrows.) The most common site identified is shown underlined. Sequence of AL3 primer is double-underlined.