(last modified February 01, 2004)
Dystrophin was discovered by ... .
The dystrophin gene maps to chromosome X (Xp21.2).
|Exon||Exon size (bp)||Intron size (kb)||5' cDNA position||Splice after||Remarks|
|1||5'UTR / .. bp coding|
Exon: numbering of exons and intron/exon boundaries are according to ..., with the first base of the Met-codon counted as position 1 (see ...reference sequence). Exon size: size of exon indicated in basepairs. Intron size: size of intron indicated in kilobasepairs. 5' cDNA position: first base of the exon (according to cDNA sequence ...). Splice after: splicing occurs in between of two coding triplets (0), after the first (1) or the second (2) base of a triplet. Remarks: 5'UTR = 5' untranslated region, 3"UTR = 3' untranslated region.
The DMD gene produces a range of different mRNA-transcripts encoding various dystrophin isoforms, i.e. proteins of varying lengths containing different segments of the basic dystrophin sequence. The isoforms are encoded by a range of different mRNA's which are generated by three processes; (i) the use of different, unique and often tissue-specific promoters, (ii) alternative splicing, and (iii) the use of different polyA-addition signals.
Tennyson et al. (1995) used quantitative RT-PCR to estimate that transcription of the 2.3 Mb DMD-gene requires approximately 16 hours (at an average elongation rate of 2.4 kb/min). Transcripts were spliced at the 5' end before transcription was complete, which provided strong evidence for co-transcriptional splicing. The rate of transcript accumulation was reduced at the 3' end relative to the 5' end, probably due to premature termination of transcription complexes (Tennyson et al. ).
When comparing the chicken and human cDNA sequences Lemaire et al.  observed a striking evolutionary conservation of three segments of the 3' untranslated region (3'UTR, 85% homology over a total of 920 nucleotides). Including the sequences from an amphibian and a cartilaginous fish Greener et al.  refined this observation to two highly conserved regions separated by a non-conserved 700-2,000 nucleotide spacer;
Dystrophin is a rod-shaped protein, measuring about 150 nm, consisting of 3684 amino acids with a calculated molecular weight of 427 kDa. Dystrophin is predominantly hydrophilic throughout its entire length and 31% of the amino-acids are charged (i.e. Arg, Asp, Glu, His and Lys). A "Chou and Fasman" prediction of secondary structure reveals a very high potential for an alpha-helical formation over the majority of the sequence. Dystrophin can be separated into four domains:
|Domain||sub domain||amino acids||exons|
|actin binding domain||14-240||2-8|
|central rod domain||253-3040||8-61|
|dystroglycan binding site||3080-3408||63-70|
|alpha1-syntrophin binding site||3444-3494||73-74|
|▀1-syntrophin binding site||3495-3535||74-75|
Dp71 is phosphorylated in vitro by p34cdc2 protein kinase Milner 93, JBC 21:21901-21905 (consensus site in exon 78 -TPGK-). Exon 1 encodes the 5'-untranslated region and 11 amino acids.
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