Organization of the human SMAD5 gene.

The boxes represent exons, and the lines denote introns. Filled boxes with jagged lines represent the partial 5′ and 3′ UTR. The SMAD5 coding region resides between the ATG start codon at exon 3 and the TAA stop codon at exon 8. The sizes of the exons are as follows: exon 3, 574 bp; exon 4, 252 bp; exon 5, 120 bp; exon 6, 222 bp; and exon 7, 257 bp. The sizes of the introns are: intron 3, 6.5 kb; intron 4, 2.1 kb; intron 5, 8.0 kb; intron 6, 1.5 kb; and intron 7, 2.5 kb. The exons corresponding to the MH1, linker, and MH2 domains are noted.