Transcription

Regulation of transcription

Distal regulatory elements: DNA sequences that can affect the transcription rate of a gene and can be located before, within, or after an intron of the gene they regulate. They may be near the gene or thousands of base pairs away
- Enhancers

Initiator met-tRNA, eukaryotic IF2 (eIF2), and GTP bind to the small ribosomal subunit to form a preinitiation complex (initially a 43s preinitiation complex).
- eIF2: a small G protein
  - Binds initiator met-tRNA (ternary complex) and forms the final initiation complex by hydrolyzing GTP to GDP
  - Reconverted to the GTP-bound form by the guanine nucleotide exchange factor eIF2B
Kozak sequence: Eukaryotic consensus sequence around the start codon that enhances initiation efficiency.

An aminoacyl-tRNA complex with eukaryotic elongation factor 1 (eEF1) hydrolyzes GTP, thereby releasing eEF1 and GDP and providing the energy for aminoacyl-tRNA to bind the A site (anticodon matches the codon of the mRNA).

A release factor recognizes the stop codon, halts translation, and hydrolytically cleaves the peptidyl tRNA bonds (requires GTP), leading to release of the protein.