Sequence of the RT1-E2n gene. The sequence was derived after subcloning the upstream 2.8 kb Pst I and 4.5 kb BamH I DNA fragments obtained by restriction digest of both the 473K19 and 303P13 PAC. Corresponding restriction sites are boxed. The coding sequence is presented in black whilst non-coding regions (introns, 5' UTR and 3' UTR) are in grey. Splice donors (GT) and splice acceptors (AG) are underlined, as well as the polyadenylation site. The fifteen nucleotides at the start of exon 6 which are boxed in dashed lines are predicted to be systematically present in the cDNAs for RT1-E2n, like those from the RT1-Eu and RT1-E2al loci because the 'canonical' second splice acceptor (AG) is mutated to AA. For E2cl and E2dl, the second splice acceptor is conserved as AG, and the corresponding 15 nucleotide segment is present in only a small proportion of the clones obtained (see Table 1).