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 INTRODUCTION
Monday, May 11, 2020

12:24 PM

- When a protein is needed in the cell, the genetic code for the amino acid sequence of that protein must be read from the
DNA and the protein made
...

• TRANSLATION
- Conversion of mRNA base seq info into the aa se of polypedpetide
...

- snRNA: with ptns form complex- used in eu
...


• Only ptn coding gene=transcribed in mRNA
• Non ptn coding gene = cannot transcribed into mRNA

introduction Page 1

PROTEIN



TRANSCRIPTION IN PROKARYOTES
Monday, May 6, 2019

8:58 PM

factor =

ensure RNApol binds in stable way
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• INITIATION
- RNA Pol holoenzyme- work from promoter sequence
...
=2α
β
and
factor ( core enz+ sigma factor = holoenzyme)
β'
help in transcription
recognize promoter seq
...
coli : promoter= 2 consesus sequence(base- most frequently found
...
)
-35=5'-TTGACA-3'
(prinbow box)
70 in E
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(-1,-2…)
- Terminator always +my in dowwnsteam region
...
RNA pol binds - consensus seq
...
Other consensus seq also there like =-10=5'-GATACT-3'
( but rate of transcription- low)
3
...
Binds = -35 seq then bnds full promoter [CLOSED PROMOTER COMPLEX]
4
...
Untwiste DNA at -10 region
5
...
Contacts: 75bb of DNA= -55 to +20
...
sigma 32 is used when gene is under heat shock or stress
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[RNApol become mores compact]
In E
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RNA pol moves alond DNA double helix… untwist it
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As ss
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Backing up once step and then replacing the incorrect nucleotide with correct ones forward step
2
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2
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- This causes - RNA pol to slow down and then pause - catalysis of RNA
- Strings of U nucleotide- downstream of hairpin -destabilise pairing between
DNA n RNA
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Rho Protein
Rho binds to the C rich seq
...
- where most recently synthesized RNA-DNA …
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Uniwinds helix using ATP hydrolysis
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- As eu
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Classes of RNA pol
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Of---

RNA pol I

nucleolus

28s rRNA
18s rRNA
5
...

- Cis region= gene expression
- Trans region= control gene expression
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Determine efficiency of transcription initiation
Eg= housekeeping enz
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: actin gene etc

•
-

Enhancers
Req
...
Start site
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transcription Page 3

•
-

Transcription of protein coding gene by RNA pol II
Eukaryotic genes transcribed by - RNA polymerase II
No specific terminator seq
...

Needed for transcription machinery to start RNA syn
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Core Promoter
i
...
TATA box/TATA elements: goldberg- hognes box
: -30
: 5'-TATAAAA-3'

-

2
...

ii
...

Promoter proximal elements
Upstream from TATA box
= -50 to -200 nts from start of transcription
...


Initiation
Involves assembly of RNA pol II + general transcription factor (GTF)
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1st GTF bind; then recruits RNA pol enz
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+

} TFIID:TATA box= ICC

TAF- TATA ass
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- A+B :ICC
- F:RNA pol II:ICC= MTIC
- E , H =PIC

Helicase…
...
and transcription Ready to
begin…

• Structure and production of eukaryotic mRNAs
- Mature biologically active mRNA= 5 'UTR +
Leader sequence

ptn coding seq
...
transcription

Eu
...
Pol residue in cytosol

as

Specific terminator seq
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RNA pol can directly binds X NOT
To DNA
Coupled transc
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separate

Polycistronic-mRNA

monocistronic

transcription Page 4

+ 3'UTR
trailer sequence

• Production of mature mRNA in eu
...
5' modification
- Pre-mRNA: 20-30nts
capping enz
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Cap remain throughout processing
protect mRNA:against degradation by exonuclease
Cap imp- binding of ribosome (initial step translation)

EXON - ptn coding gene+ premRNA~ specifies aa
- expressed seq
...


2
...

- protects 3' end from degradation by exonuclease
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CPSF-cleavage and polyadenylation factor
- bind to consensus seq
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CstF-cleavage stimulating factor
- bind to GU or U rich seq
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iii
...
PAP-poly A polymerase
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v
...
mRNA and intron
removal by the spliceosome
= 5' cap---i+e----3'poly A tail
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- Introns: begin with 5'-GU
: end with AG-3'
- mRNA splicing= intron removal +exon joining
- This occur in spliceosome: pre-mRNA + snRNPs
- snRNPs- snRNA+ PTN

transcription Page 6

•
-

Self splicing introns
Ptn independent reaction
RNA folds into 2° str - promote own excision
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