Biochimica - trascrizione

La Trascrizione

RNA polymerase

promoter

stop signal for RNA polymerase

DNA double helix

DNA helix opening

start site for transcription

initiation of RNA chain by joining of first two ribonucleoside triphosphates

RNA chain elongation in 5'-to-3' direction by addition of ribonucleoside triphosphates

continuous RNA strand displacement and DNA helix re-formation

short region of DNA/RNA helix

termination and release of polymerase and completed RNA chain

La Trascrizione

• RNA polymerase
• promoter
• stop signal for RNA polymerase
• DNA double helix
• DNA helix opening
• start site for transcription
• INITIATION OF RNA CHAIN BY JOINING OF FIRST TWO RIBONUCLEOSIDE TRIPHOSPHATES
• RNA CHAIN ELONGATION IN 5'-TO-3' DIRECTION BY ADDITION OF RIBONUCLEOSIDE TRIPHOSPHATES
• continuous RNA strand displacement and DNA helix re-formation
• short region of DNA/RNA helix
• TERMINATION AND RELEASE OF POLYMERASE AND COMPLETED RNA CHAIN

La Trascrizione

• RNA polymerase
• stop signal for RNA polymerase
• promoter
• DNA double helix
• DNA helix opening
• start site for transcription
• INITIATION OF RNA CHAIN BY JOINING OF FIRST TWO RIBONUCLEOSIDE TRIPHOSPHATES
• RNA CHAIN ELONGATION IN 5'-to-3' DIRECTION BY ADDITION OF RIBONUCLEOSIDE TRIPHOSPHATES
• continuous RNA strand displacement and DNA helix re-formation
• short region of DNA/RNA helix
• TERMINATION AND RELEASE OF POLYMERASE AND COMPLETED RNA CHAIN

La sintesi dell’RNA segue la regola della complementarietà delle basi

growing RNA chain

DNA template strand

incomig ribonucleoside triphosphate

5'-to-3' direction of chain growth

L’RNA polimerasi

1. Binding of RNA polymerase
2. Separation of DNA
3. Base pairing of first nucleoside triphosphate to starting base in DNA
4. Binding of second nucleoside triphosphate and formation of phosphodiester bond between its 5' phosphate and the 3' hydroxyl on previous nucleotide
5. Binding and addition of third nucleoside triphosphate; continuation of process with each successive nucleoside triphosphate, as RNA polymerase moves along template DNA

Il “Footprint”

-DNA-binding protein

Protein-binding sequence

+DNA-binding protein

Sequence-specific binding protein

Footprint

Footprinting lanes

Sequencing lanes

A

G

T

C

L’inizio di trascrizione nei batteri

Speciali sequenze di DNA indicano l'inizio e la fine della trascrizione

(A) START SIGNAL

5'—T A T G T G A T T A G C A G A T G A G A G C T C A T C T C A A T A T G G T C C A C G —3'

3'—A T C A C A T A A T C G T C T A C T C T C G A G T A G A G T T A T A C C A G G T G C —5'

5' DNA

3' DNA

DNA template strand

start sito

TRANSCRIPTION

5' AGGUCCACG 3' RNA

(B) STOP SIGNAL

5'— C C C A C A G C C C G G A C T C C G G C G G C G A T T A A C T C T T T T A A T G A—3'

3'—G G G T G T C G G G C C T G A G G C C G C C G C T A A T T G A G A A A A T T A C T—5'

DNA template strand

TRANSCRIPTION

5'—C C C A C A G C C C G G A C U C C G G C G G C G A U U U U U C G G C G G A G U C C G G G U G G G C 3' OH

RAPID RNA FOLDING

U U C G C

folded

RNA chain

helps cause

chain termination

5'—C C C A C A

U U U U 3' OH

Un solo filamento è trascritto

an RNA polymerase that moves from right to left makes RNA by using the top strand as a template

DNA double helix

an RNA polymerase that moves from left to right makes RNA by using the bottom strand as a template

I Promotori

(a) Strong E. coli promoters