Figure 6.

(A) Nucleotide sequence of intron 4 of human Dnmt1 gene. Only the coding strand is shown; exon 4, exon 5, and locations of different Alu family repeats within the intron are indicated. The sequence of approximately 300 bp (in parentheses) between Alu2 and Alu3 could not be determined accurately. The 7-bp sequence in Alu4 is also uncertain. The direct repeats flanking Alu3 and the tetrameric array composed of Alu4, Alu5, Alu6, and Alu7 are in individual boxes. (B) Alignment of the seven Alu family repeats of human Dnmt1 intron 4 and the Alu consensus sequence (Alu co.). Only sequences of the antisense strands are shown. The numbering follows that used for the Alu consensus in ref. 33. The segment of Alu1 is shown in full. Nucleotides identical to Alu1 are represented by the vertical bar. Relative deletions are indicated by hyphens. Note that Alu5 is only half the length of a typical monomeric Alu repeat and could have resulted from deletion via homologous recombination within an ancestral Alu sequence. The 48 nt in Alu1 that could be alternatively spliced to generate Dnmt1-b RNA are indicated by bold letters. Also shown above the junction between this 48-nt segment and its flanking regions are the consensus sequences of the acceptor and donor sites for eukaryotic mRNA splicing.