Recognize promoter and determine transcription specificity (only functions in the initial stage, after RNA synthesis is initiated, it immediately falls off from the holoenzyme and can be reused)

Different sigma factors recognize different promoters and express different genes. Different from promoter binding ability, transcription efficiency is different.

The strong binding between the α subunit and the promoter locally unwinds the DNA double strands.

β subunit catalyzes phosphodiester bond formation; (elongation of RNA chain)—replication

β' subunit participates in template strand binding

-10 sequence, binding site, sequence is TATAAT

Rich in AT, dissolves the double helix and forms a promoter complex with RNA polymerase

-35 sequence, recognition site (providing recognition signal for RNA polymerase), the sequence is TTGACA

The σ subunit recognition site determines the strength of the promoter, transcription speed, and protein synthesis speed (the speed and strength are controlled by the σ recognition site)

Hat site: starting point (1), base A

TATA box: -25, GC rich, binding site, similar to P,

CAAT box: -75, controls the frequency of transcription initiation

universal transcription factor

1. RNA polymerase binds to the promoter through the recognition site (-35 region) to form a closed initiation complex; 2. Moves and binds to the binding site (-10) to form an open initiation complex; 3. The β subunit forms a phosphodiester bond to form an enzyme-DNA-RNA ternary complex, and transcription initiation is completed.

σ recognition, after the formation of a stable ternary complex (after transcription initiation), the σ factor is immediately shed

Beta factors play a major role in forming RNA-DNA hybrids

Non-constant speed, there will be a pause when encountering GC-rich bases

terminator

ρ factor

A DNA sequence that is on the same DNA molecule as the related gene and regulates gene transcription - cis-regulation, no product is transcribed; upstream of the 5' end, downstream of the 3' end, inside the gene

promoter, enhancer, silencer, insulator

Cutting: Cut the primary product into 5S, 16S, and 23S fragments

Modification: Methylation of ribose 2' hydroxyl group

Cutting: RNase P, removes excess nucleotides

Modification: base methylation and addition of CCA to the 3' end

Pre-mRNA---Nuclear heterogeneity---RNA (hnRNA)---Mature mRNA

hnRNA---mRNA: 5' capping, 3' tailing, splicing

5' capping cap structure: N7-methylguanylate 5',5'-triphosphate bond

3' tail: polyadenylic acid (polyA)

splicing

Eukaryotic cell processing (capping, tailing, splicing) is a continuous process, and transcription and processing occur simultaneously

prokaryotes clover structure

1. Endonuclease cuts two sections of tRNA; 2. Endonuclease cuts off nucleotides one by one from the 3' end and trims them; 3. Adds -CCA to the 3' end; 4. Modification

RNA self-splicing (Tetrahymena RNA): Discovered that RNA has catalytic activity and proposed the concept of ribozymes

Eukaryotic cell methylation: tRNA is carried out on the base, rRNA is carried out on the 2' hydroxyl group of ribose