The evolution of an intron: analysis of a long, deletion-prone intron in the human dystrophin gene.
The sequence of a 112-kb region of the human dystrophin (DMD/BMD) gene encompassing the deletion prone intron 7 (110 kb) and the much shorter intron 8 (1.1 kb) has been determined. Recognizable insertion sequences account for approximately 40% of intron 7. LINE-1 and THE-1/LTR sequences occur in intron 7 with significantly higher frequency than would be expected statistically while Alu sequences are underrepresented. Intron 7 also contains numerous mammalian-wide interspersed repeats, a diverse range of medium reiteration repeats of unknown origin, and a sequence derived from a mariner transposon. By contrast, the shorter intron 8 contains no detectable insertion sequences. Dating of the LI and Alu sequences suggests that intron 7 has approximately doubled in size within the past 130 million years, and comparison with the corresponding intron from the pufferfish (Fugu rubripes) suggests that the intron has expanded some 44-fold over a period of 400 million years. The possible contribution of the insertion elements to the instability of intron 7 is discussed.
McNaughton
J C
JC
Department of Biochemistry, University of Otago, Dunedin, New Zealand.
Hughes
G
G
Jones
W A
WA
Stockwell
P A
PA
Klamut
H J
HJ
Petersen
G B
GB
D001482:Base Composition; D016189:Dystrophin / Q000235:genetics*; D019143:Evolution, Molecular; D005796:Genes / Q000235:genetics; D006801:Humans; D007438:Introns / Q000235:genetics*; D008969:Molecular Sequence Data; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D017384:Sequence Deletion / Q000235:genetics
D016189:Dystrophin