Transcription requires several key components. The essential items are DNA (as the template), the enzyme that synthesizes RNA, and the building blocks for RNA. Here’s a concise list focused on the core requirements: Core requirements
- DNA template: Provides the sequence to be transcribed.
- RNA polymerase: The enzyme that catalyzes RNA synthesis by reading the DNA template.
- Nucleoside triphosphates (rNTPs): The building blocks (adenine, uracil, cytosine, guanine) supplied as ribonucleoside triphosphates to assemble the RNA strand.
- Promoter region (in the gene): The DNA sequence where RNA polymerase binds to initiate transcription.
- Accessory factors (in many organisms): Additional proteins or transcription factors that assist RNA polymerase in locating the promoter, initiating, and elongating (especially in eukaryotes).
Optional but important stages and features
- Initiation complex formation: RNA polymerase binds promoter and forms the transcription initiation complex.
- Template strand alignment and unwinding: The DNA region around the start site unwinds to expose the template.
- Elongation: RNA polymerase reads the template and extends the RNA chain in the 5' to 3' direction.
- Termination signals: Sequences that signal transcription to stop, releasing the newly formed RNA.
- Post-transcriptional processing (primarily in eukaryotes): Modifications such as 5' capping, 3' poly-A tail addition, and splicing to produce mature mRNA.
Notes
- Ribosomes, tRNA, and amino acids are not direct requirements for transcription; they participate in translation after transcription completes.
- The exact set of auxiliary factors varies between prokaryotes and eukaryotes, but the core trio—DNA template, RNA polymerase, and RNA precursors—remains essential.
