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Nested introns in an intron: Evidence of multi‐step splicing in a large intron of the human dystrophin pre‐mRNA
Author(s) -
Suzuki Hitoshi,
Kameyama Toshiki,
Ohe Kenji,
Tsukahara Toshifumi,
Mayeda Akila
Publication year - 2013
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2013.01.057
Subject(s) - intron , rna splicing , group ii intron , biology , genetics , splice site mutation , splice , gene , rna
The mechanisms by which huge human introns are spliced out precisely are poorly understood. We analyzed large intron 7 (110 199 nucleotides) generated from the human dystrophin (DMD) pre‐mRNA by RT‐PCR. We identified branching between the authentic 5′ splice site and the branch point; however, the sequences far from the branch site were not detectable. This RT‐PCR product was resistant to exoribonuclease (RNase R) digestion, suggesting that the detected lariat intron has a closed loop structure but contains gaps in its sequence. Transient and concomitant generation of at least two branched fragments from nested introns within large intron 7 suggests internal nested splicing events before the ultimate splicing at the authentic 5′ and 3′ splice sites. Nested splicing events, which bring the authentic 5′ and 3′ splice sites into close proximity, could be one of the splicing mechanisms for the extremely large introns.