Complete Dnmt cDNA contains two
additional 5′ exons that extend the ORF by up to 171 codons.
(A) Comparison between murine and human Dnmt
sequences at the 5′ end. New sequence reported in this paper is shown
in uppercase type and the previously reported sequence is in lowercase
type. The first two rows of sequence are genomic sequence, while the
five rows beneath represent cDNA sequence. A previously reported human
cDNA (31) is shown beneath the murine sequence with all matches
represented by a vertical bar. A predicted translation of the 182-codon
extension of the ORF is shown above the murine nucleotide sequence,
starting with the stop codon TAG and with the four methionine residues
boxed. Differences in the human amino acid sequence are represented
beneath the human nucleotide sequence. Vertical bars running through
the murine sequence denote exon–exon boundaries, with the numbers
corresponding to the exon designations used in B. The
two boxed sequences represent the primers MMT2214AS (box 1) and
MMT2363AS (box 2) used in the cloning experiments. The
EcoRI site that marks the beginning of the
Dnmt cDNA used in the expression constructs in Fig. 1 is
indicated by a bar over the recognition sequence. The major
transcriptional start site found by Rouleau et al. (15)
is indicated by a vertical arrow. (B) Map of exonic
structure of the 5′ end of Dnmt. The first four exons of
Dnmt are represented to scale with respect to their size
and relative position in the gene. Exon numbers described in text are
given above. The splicing of the first four exons of
Dnmt is diagrammed above, while the alternative splicing
observed in mouse testis (N. B. Kuemmerle, L. E. Halce, and K.
Valerie, unpublished work) is shown below. The numbering of the
nucleotide scale starts with 0 as the 5′ end of the new cDNA sequence.
The two alternative exons are separated from the second common exon by
a 10-kb interval of genomic DNA, indicated by the broken lines in the
splicing diagram. CpG and GpC incidence diagrams are plotted below to
scale with the rest of the diagram. The two 3′-proximal ATGs indicated
by a boxed M in A are shown in their genomic locations,
while the first two ATGs are indicated by vertical arrows to the left
of exon 1. The major transcriptional start site found by Rouleau
et al. (15) is indicated by a horizontal arrow below
exon 3.