1. There are four main classes of RNA: ribosomal RNA, messenger RNA, transfer RNA, and small nuclear RNA. 2. Transcription involves three stages - initiation, elongation, and termination. It uses DNA as a template to produce RNA. 3. Eukaryotic transcription requires RNA polymerase and other transcription factors to initiate transcription from a promoter region on DNA. The transcription process includes initiation, elongation, and termination.

2. Key classes of RNA
1.Ribosomal RNA (80%)– functions as
structural and enzymatic component of
ribosomes.
2.Messenger (informational) RNA (5%)–
acts as intermediate between genetic code and
amino acid sequence of proteins
3.Transfer RNA (15%) – adapter molecule
that carries amino acid to specific codon on
mRNA in ribosome during protein synthesis.
4.Small nuclear RNA (snRNA) and proteins
form spliceosome.

4. Transcription
Template – one strand of the double-
stranded DNA.
The DNA template is copied in the 3’-
to-5’ direction, and the RNA transcript is
synthesized in the 5’-to-3’.
The strand that serves as a template
has name template strand.
The other strand, while not used as a
template, is called the coding strand.

5. 1. Substrates – ribonucleoside thiposphates (ATP,
GTP, CTP, UTP).
2. Sources of energy–substrates (ATP, GTP, CTP,
UTP).
3. Enzymes – RNA polymerases (RNAP).
 Defferences between DNAP and RNAP
1. No primer is needed in RNA
2. No proofreading activity in RNAP
* RNA Pol I – rRNA;
* RNA Pol II –mRNA;
* RNA Pol III – tRNA.
Transcription protein factors.
4. Product – pre-tRNA, pre-mRNA, pre-rRNA.
5. Localization in the cell - nucleous

6. Architecture of RNA polymerase II.
Transcription of DNA (helical structure) into RNA
(red) is shown.
The template strand of DNA is shown in blue and
the coding strand in green.

7. Transcription
Three major stages:
1. Initiation.
2. Elongation.
3. Termination.

8. Transcription
Initiation
DNA molecule

9. Promoters of Trancription
Short conserved sequence
in the cording strand of DNA
that specifies start site of
the transcriotion.
They are generally called as
box or element

10. Distal regulatory elements
• Enhancers, silencers
Promoter proximal upstream elements
СААТ-box, GС-box
Promoter
• TATA box
Py = pirimidine

11. Distal regulatory elements
• Enhancers, silencers
DNA Elements that facilate or
enhance initiation at the promoter are
enhancers.
They have multiple binding sites
for transcription activator proteins.
Silencers have opposite function.

12. Кафедра биохимии и фармакологии БелГУ

13. Eukariotic transcription require certain
proteins apart from RNAP-Trancription
factors (TF)
 Pre-Initiation complex formation
require RNAPII and 6 TF (TFIIA,
TFIIB, TFIIE, TFIIF, TFIIH – 5
factors; TFIID)
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14. Initiation
 Eucariotic pol II doesn’t recognize and bind to
the promoter by itself.
 TFIID binds to TATA box through its TBP
(TATA binding protein).
 Then 5 factors and RNA pol II binds to
complex of DNA+TFIID

15.  TFIIH is ATP-depended helicase
which unwinds promoter and pulls
the strands into active site of RNA
pol II
 After that duplex unwinding and
rewinding are carring out by RNA
pol II
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16. Elongation
 RNA pol II undergoes comformation
changes (it is phosphorilated by kinase
component of TFIIH)
 Due to this PNA pol II lost affinity to TF
and they dissociate from it
 Elongation transcription factors bind to it
 After this enzyme is active and canalizes
formation of RNA strand
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17. Termination
 Termination site is recognized by
termination factors.
 When they attach to this site RNA pol
dissociates from DNA and newly formed
RNA is realised
 Primary trascript (pre-m-RNA) is ofthen
larger than mature mRNA

18. Promoter Site of termination
DNA
DNA
TATA binding protein
RNA pol
Elongation factors
Termination factors
RNA pol
Pre-RNA
Regulatory factors
RNA transcript
Initiation factors

19. Кафедра биохимии и фармакологии БелГУ
Post-trancriptional processing pre-m-RNA
Three stages:
1. Capping at 5’ end (occurs shortly
after initiation when 30 nucleotide
residues are including into growing
chain).
2. Poly-A tailing at 3’end. (after end
of trascription)
3. Removal of introns. (after end of
trascription)

20. 7-methylguanine triphosphate (cap)
Nitrogenous
base
mRNA

21.  A.GTP is attached to the 5 end of pre-mRNA
by Guanylyl tranferase by an unusual 5-5
triphosphate linkage
Takes place inside the nucleus
 B. Methylation of GTP by Guanine-7 methyl
tranferase
 S-adenosyl Methionin is the methyl donor
Takes place inside the cytosol

22. Functions of capping:
1. Helps to stabilize mRNA
2. Permits initiation of translation
3. Protects the mRNA from degradation
by exonucleases

23. 1. Facilitates exit of mRNA from the
nucleous.
2. Protects the mRNA from degradation by
exonucleases.
PolyA tail consists of 100-200 residues of adenylic acid
Polyadenylate polymerase, nucleus
polyA-sequencemRNA
3’end
Poly-A tailing at 3’end.
Functions:

25. Splicing

26.  Spliceosome consists of primary
trancript, 5 small nuclear RNAs
(uracil rich RNA which are
ribozymes) and more than 60
proteins