Pathway · 8 proteins
Transcription
RNA polymerase and transcription factors produce RNA from DNA.
How it works
- A bacterial RNA polymerase and appropriate initiation factors recognise a transcription start region.
- RNA polymerase reads the template and joins ribonucleotides to extend RNA.
- Termination releases the transcript. Its subsequent maturation and use depend on whether the RNA is mRNA, rRNA, tRNA or another functional RNA.
Grouped by the atlas’s curated pathway map. The table order is not a proven reaction order.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| DNA-directed RNA polymerase subunit alpha | 2.7.7.6 | RNA(n) + a ribonucleoside 5'-triphosphate = RNA(n+1) + diphosphate | — | 317 | Step named |
| Transcription antitermination protein NusB | — | — | — | 148 | Step named |
| RNA polymerase sigma factor SigA | — | — | — | 575 | Step named |
| Transcription termination/antitermination protein NusG | — | — | — | 248 | Step named |
| DNA-directed RNA polymerase subunit beta | 2.7.7.6 | RNA(n) + a ribonucleoside 5'-triphosphate = RNA(n+1) + diphosphate | — | 1468 | Step named |
| DNA-directed RNA polymerase subunit beta' | 2.7.7.6 | RNA(n) + a ribonucleoside 5'-triphosphate = RNA(n+1) + diphosphate | Zn(2+), Mg(2+) | 1574 | Step named |
| Transcription termination/antitermination protein NusA | — | — | — | 337 | System only |
| Transcription termination factor Rho | 3.6.4.- | ATP + H2O = ADP + phosphate + H(+) | Mg(2+) | 436 | Step named |
Origins
How could genes be read into RNA before RNA polymerase existed?
The books searched say little about a prebiotic route to transcription. Subunits of RNA polymerase are among the most conserved proteins in all cells.
RNA polymerase is itself a protein, made by translating RNA that RNA polymerase made: the reader of the genes is encoded in the genes it reads.
In bacteria the core enzyme of several subunits finds the start of a gene only with a sigma factor that recognises the promoter sequence. Eight proteins of the minimal set serve transcription.
From the books: Koonin, The Logic of Chance, PDF p. 34.
The wider question for this part of the cell: origins for reading genes into rna.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: RNA processing and turnover · DNA replication · Not yet placed in a pathway