Rates of in situ transcription and splicing in large human genes.
Transcription and splicing must proceed over genomic distances of hundreds of kilobases in many human genes. However, the rates and mechanisms of these processes are poorly understood. We have used the compound 5,6-dichlorobenzimidazole 1-beta-D-ribofuranoside (DRB), which reversibly blocks gene transcription in vivo, combined with quantitative RT-PCR to analyze the transcription and RNA processing of several long human genes. We found that the rate of RNA polymerase II transcription over long genomic distances is about 3.8 kb min(-1) and is similar whether transcribing long introns or exon-rich regions. We also determined that co-transcriptional pre-mRNA splicing of U2-dependent introns occurs within 5-10 min of synthesis, irrespective of intron length between 1 kb and 240 kb. Similarly, U12-dependent introns were co-transcriptionally spliced within 10 min of synthesis, confirming that these introns are spliced within the nuclear compartment. These results show that the expression of large genes is unexpectedly rapid and efficient.
Singh
Jarnail
J
Department of Molecular Genetics, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA.
Padgett
Richard A
RA
D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D005091:Exons / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000235:genetics; D006801:Humans; D007438:Introns / Q000235:genetics; D007700:Kinetics; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism; D012326:RNA Splicing / Q000235:genetics*; D012342:RNA, Small Nuclear / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*; D049411:Utrophin / Q000235:genetics
D019384:Nucleic Acid Synthesis Inhibitors; D012342:RNA, Small Nuclear; C096986:U12 small nuclear RNA; D049411:Utrophin; D004004:Dichlororibofuranosylbenzimidazole; D012319:RNA Polymerase II; D020558:GTP Phosphohydrolases; C415198:OPA1 protein, human