Fig. 3. Dmkp3 genomic organization, alleles, protein structure and expression. (A) The Dmkp3 gene consists of five exons and is characterized by a large intron and extensive 5' and 3' UTRs (open rectangles). A putative alternative (incomplete) transcript is denoted and the site of the Dmkp3⁵ splice-acceptor mutation is indicated (arrowhead). EP insertion sites and orientations are symbolized by wands. (B) The DMKP3 protein has three human functional homologs: MKP-3, MKP-4 and MKP-X, which are 52-58% similar. MKP-X sequence has been delineated from partial cDNAs. Underlined are the N-terminal Cdc25-homology (CH2) domain implicated in MAPK binding (gray) and the C-terminal catalytic domain (black). The broken line marks the ERK docking motif and the dotted line the core catalytic site. These central sites are presumably disrupted in the DMKP3⁷ and DMKP3¹⁰ gene products. With the possible exception of Dmkp3⁶, the other alleles are null mutations as well (see amino-acid replacements and allele numbers above the alignment). The arrow marks the site of the Dmkp3⁵ mutation. (C) Dmkp3 is weakly expressed just posterior to the morphogenetic furrow. Negative and positive controls are shown in D and E, respectively.

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