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1. TRANSCRIPTION. 2. TRANSCRIPTION RNA STRUCTURE, SYNTHESIS, AND FUNCTION Kinds of RNA transfer, ribosomal, messenger Structure single-stranded, partial double-strand regions, H bonds RNA Polymerase Promoter reading frame, closed complex, open complex, initiation

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Presentation Transcript
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TRANSCRIPTION

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TRANSCRIPTION

RNA STRUCTURE, SYNTHESIS, AND FUNCTION

Kinds of RNA transfer, ribosomal, messenger

Structure single-stranded, partial double-strand regions, H bonds

RNA Polymerase

Promoter reading frame, closed complex, open complex, initiation

Specificity Factor sigma

Polymerization single strand 5' > 3'

Termination

Eukaryotic mRNA exon, intron, capping, poly A, splicing

RNA POLYMERASE ACTIVITY SUBJECT TO:

Specificity factors sigmas which recognize specific promoters

Accessory factors repressors, activators, anti-sense RNAs, anti-sigma factors

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3

GENE PRODUCTS INCLUDE:

PROTEIN

OR

RNA

GENES (DNA)

TRANSCRIPTION BY

RNA POLYMERASE

mRNA

or rRNA or tRNA

TRANSLATED INTO

PROTEINS

FUNCTION IN

PROTEIN SYNTHESIS

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URIDINE TRIPHOSPHATE - UTP

ESTER

URACIL

N - GLYCOSIDE

BOND

ANHYDRIDES

NUCLEIC ACID BASE

RIBO NUCLEOSIDE

RIBO NUCLEOSIDE TRIPHOSPHATE

OR: RIBONUCLEOTIDE

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RNA STRUCTURE

SINGLE STRANDS

COMPLEMENTARY REGIONS FOLD BACK

PARTIALLY

DOUBLE-STRANDED

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[POLYCISTRONIC]

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RNA POLYMERASE + PROMOTER

CLOSED COMPLEX

DOUBLE STRAND

OPEN COMPLEX

PROMOTER UNWOUND

RNA POLYMERASE

SUBUNITS

a2bb' s

CORE - POLYMERIZATION

INITIATION (SPECIFICITY) FACTOR

HOLOENZYME

FUNCTIONS : RECOGNIZE/BIND

SUBSTRATES - ATP, GTP, UTP, CTP

PROMOTER - SITE IN DNA

TEMPLATE - TRANSCRIBES NUCLEOTIDE SEQUENCE

INITIATION OF POLYMERIZATION

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PROMOTER - SITE IN DNA

RNA POLYMERASE BINDS; STARTS TRANSCRIPTION

-35

-10

+1

5'

3'

3'

5'

5'

3'

3'

5'

ONE DNA STRAND IS TEMPLATE (TRANSCRIBED)

RNA SEQUENCE - COMPLEMENTARY TO LOWER DNA STRAND;

IDENTICAL TO TOP STRAND (EXCEPT U FOR T)

RNA - POLYMERASE STARTS CHAINS

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RNAPOLYMERIZATION

3'

5'

DNA TEMPLATE

3'

3'

5'

5'

NUCLEOTIDYL

TRANSFER

3'

5'

NOTE 5' 3'

+

3'

3'

5'

5'

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GENE OR OPERON

PROMOTER

TERMINATOR

5'

3'

3'

5'

TRANSCRIPTION

START

TRANSCRIPTION

STOP

RNA POLYMERASE

HOLOENZYME - CORE + s

RNA POL

CLOSED COMPLEX

CORE + s

OPEN COMPLEX

ATP/GTP/UTP/CTP

3'

5'

INITIATION

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PPi +s

ATP/GTP/UTP/CTP

3'

3'

5'

POLYMERIZATION

5'

3'

3'

5'

5'

3'

5'

TERMINATION

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TERMINATOR STEM AND LOOP

COMPLETED mRNA

PROTEIN CODING REGION

PROTEIN READING FRAME

5'

3'

UNTRANSLATED REGION

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GENE OR OPERON

PROMOTER

TERMINATOR

5'

3'

3'

5'

TRANSCRIPTION

START

TRANSCRIPTION

STOP

TRANSLATION START

TRANSLATION STOP

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GROWTH IS

DYNAMIC

PROCESS –

REPLICATION

&

TRANSCRIPTION

GO ON

SIMULTANEOUSLY

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EUKARYOTE M-RNA PROCESSING

+1-TRANSCRIPTION

START

TRANSLATION

STOP

TRANSCRIPTION

STOP

TRANSLATION

START

DNA

POLY A ADDITION SITE

PROMOTER

NON - PROTEIN CODING

INTRON

PROTEIN CODING

EXON

PRIMARY TRANSCRIPT PRE-M-RNA

5'

3'

EXON

INTRON

5' CAPPING

3' POLY ADENYLATION

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AAAA A

AAAA A

5'

3'

CAP

SPLICING

(SPLICEOSOME)

POLY-A

MATURE M-RNA

PROTEIN CODING REGION

[CONTIGUOUS CODONS]

TRANSLATION

PROTEIN

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CAP

3'

CAP FUNCTIONS -

STABILITY

DIRECT RIBOSOMES TO START CODON NEAREST CAP

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TRANSCRIBING RNA POLYMERASE II (YEAST) CUT AWAY

  • ENTERING DNA BINDS CLEFT (POSITIVE CHARGES)
  • CLAMP FOLDS OVER
  • TEMPLATE AND NON - TEMPLATE STRANDS SEPARATED
  • WALL BENDS DNA TEMPLATE 90o , EXPOSES RNA 3' END
  • Mg2+ ACTIVE SITE
  • SUBSTRATE NTPs ENTER FUNNEL AND PORE
  • RNA: DNA 9 BP HYBRID
  • RUDDER SEPARATES RNA: DNA HYBRID

TRANSCRIPTION

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TAKE HOME:

RNA POLYMERASE SEPARATES DNA DOUBLE HELIX AND COPIES NUCLEOTIDE SEQUENCE OF GENES FROM ONE STRAND OF DNA INTO COMPLEMENTARY STRAND OF RNA.

WHY?

FOR LIFE TO GO ON, INCLUDING PRODUCTION OF DESCENDANTS, THE GENETIC PROGRAM OF THE CHROMOSOME MUST BE RUN. THE FIRST STEP IS TO COPY THE NUCLEOTIDES SEQUENCE OF EACH GENE INTO MESSENGER RNA. THE SECOND STEP WILL BE TO USE THE MESSENGERS FOR SYNTHESIS OF ALL PROTEINS, INCLUDING ENZYMES AND STRUCTURAL PROTEINS, NECESSARY TO CATALYZE ALL REACTIONS OF LIFE AND TO FORM ALL THE CELL STRUCTURES.

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RNA POLYMERASE ACTIVITY

  • SPECIFICITY - DEPENDS ON SIGMAs
    • DIFFERENT SIGMA FACTORS ALLOW CORE ENZYME TO TRANSCRIBE DIFFERENT SETS OF GENES
    • DIFFERENT SETS OF GENES HAVE DIFFERENT PROMOTERS

RECOGNIZED BY DIFFERENT SIGMA FACTORS

    • E. COLI HAS 7 SIGMAs

ACCESSORY PROTEINS MODULATE ACTIVITY OF RNA POLYMERASE AND SIGMA - REGULATE LEVEL

  • INCLUDE REPRESSORS AND ACTIVATORS
  • ANTI - SENSE RNA
  • ANTI - SIGMA FACTORS