transcription
Transcription is performed by three different RNA polymerases in eukaryotic cells:
RNA polymerase I transcribes ribosomal DNA into ribosomal RNA used in the biogenesis of ribosomes;
RNA polymerase II transcribes genes into mRNA;
RNA polymerase III synthesizes transfer RNA and small nuclear RNA.
Although RNA polymerase I and III transcribe DNA at a high rate, the genomic length of DNA transcribed is rather small compared with the length of all mRNA genes transcribed by RNA polymerase II. RNA polymerase II would be expected to ?scan? a much larger portion of the genome than RNA polymerase I and III, and could therefore be considered to be a ?better? sensor than the two other RNA polymerases.
Transcription and DNA lesions
When RNA polymerase II complexes are blocked at sites of DNA lesions, they are able to recruit DNA-repair proteins to perform transcription-coupled repair (TCR), a specialized nucleotide-excision repair (NER) pathway that removes transcription-blocking lesions and that does not seem to be associated with RNA polymerase I or III. RNA polymerase II is perfectly suited to act as a sensor of DNA perturbations in the template and to alert the cell by activating DNA-damage signalling pathways.
Pathology
chromatin remodeling disorders
trichothiodystrophy
Pathology of Swi/Snf family of nucleosome-remodeling complexes
- rhabdoid tumor syndrome (INI1/SNF5)
See also
transcription factors
transcription machinery
transcription networks
transcriptional derepression
References
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