1) Regulation of gene expression in eukaryotes involves two main stages: transcription and translation. 2) Transcription involves RNA polymerase binding to DNA along with transcription factors at the promoter region, unwinding of DNA, and synthesis of RNA from the template strand. 3) Translation occurs in the cytoplasm using ribosomes and mRNA as a template to synthesize proteins based on the mRNA sequence, beginning with initiation at the start codon through elongation and termination at a stop codon.

1. Regulation of gene expression
in eukaryotes
Presented by- sayali kelkar
Regd. No. 2425

2. • It involves 2 stages-
1) Transciption-
2)Translation-

4. Mechanism of transcription
1)Pre initiation stage-
– RNA polymerase binds to DNA along with co
factors
– Unwinds DNA – initiation bubble.
– Core promotors- TATA promotors are found
around 30 bp to the start site of transcription.

6. 2)Initiation
– Transcription factors mediate binding of RNA
polymerase to core promotors.
– Only after that RNA polymerase bind to
promotors.
– Transcription initiation complex- RNA
polymerase+ Transcription factors+ promotor.
– Initiation starts when TIC opens and first
phosphodiester bond is formed.

8. • RNA polymerase2 does not have subunit to
recognize promotor, hence it has set of
proteins called general transcriptional factors-
TF2A, TF2B, TF2D, TF2E, TF2F, TF2H.
• TF2D consist of TATA box binding protein and
its associated factors.
• The role of TBP is to bind core promotor.
• TF2H catalyses the DNA melting.

10. 3) Elongation-
- template strand
- RNA polymerase uses base pairing
complementary to the template strand to
synthesis of RNA.
- After pre initiation complex is assembled
at promotor, TF2H use its helicase activity to
unwind DNA.

11. 4) Termination-
- cleavage of new transcript
- template independent addition of adenine
at its 3’ end- polyadenylation.
- eukaryotic protein genes contain poly A
signals which are used to add series of adenines
during RNA processing.

12. Mechanism of translation
• It occours in cytoplasm.
• 60s and 40s subunits of ribosomes are used.
• mRNA is used as template.
• Start codon- AUG
• Stop codon- UAA, UGA, UAG.
• Starting amino acid is methionine.

13. 1) Initiation- ( cap dependent)
• It involves interaction of certain proteins to
special tag bound to 5’ end of mRNA molecule.
• Eukaryotic inition factor 3- eIF3 is associated with
40s subunit.
• eIF3 interacts with eIF4 complex ( eIF4A, E, G)
• eIF4E binds to 5’ end of RNA.
• eIF4A is ATP dependent RNA helicase.
• Poly- A binding protein – circularization of mRNA
during translation.
• The pre initiation complex ( 4os subunit + mRNA)
along with protein factors move to 3’ end.
• It scans for start codon AUG from which protein
synthesis starts.

14. • Amino acid encoded by start codon is
methionine.
• The initiator tRNA charged with mithionine is
brought to p- site of 40s subunit by eIF2
factor.
• It hydrolyses GTP and signals for dissociation
of several IFs from 40s subunit and it results
in association of 60s subunit.

15. 2) Elongation-
- depends on eukaryotic elongation factors.
- mRNA is positioned such that next codon can
be translated during protein synthesis.
- iniator tRNA – p site.
- A site is ready to receive aminoacyl tRNA.
- During elongation each additional amino acid is
added to polypeptide chain-1) positioning of
aminoacyl tRNA at A site. 2) forming peptide bond.
3) shifting mRNA by one codon relative to the
ribosome.
- in such way proteins are synthesized.

16. 3) Termination
- one of the 3 stop codons move to A site.
- these codons are not recognized by tRNA.
- there is eukaryotic release factor which
recognizes all 3 stop codons.