Cn. Tennyson et al., THE HUMAN DYSTROPHIN GENE REQUIRES 16 HOURS TO BE TRANSCRIBED AND IS COTRANSCRIPTIONALLY SPLICED, Nature genetics, 9(2), 1995, pp. 184-190
The largest known gene is the human dystrophin gene, which has 79 exon
s spanning at least 2,300 kilobases (kb). Transcript accumulation was
monitored from four regions of the gene following induction of express
ion in muscle cell cultures. Quantitative reverse transcription-polyme
rase chain reaction (RT-PCR) results indicate that approximately 12 h
are required for transcription of 1,770 kb (at an average elongation r
ate of 2.4 kb min(-1)), extrapolating to a transcription time of 16 h
for the complete gene. Accumulation profiles for spliced and total tra
nscript demonstrated that transcripts are spliced at the 5' end before
transcription is complete providing strong evidence for cotranscripti
onal splicing. The rate of transcript accumulation was reduced at the
3' end of the gene relative to the 5' end, perhaps due to premature te
rmination of transcription complexes.