This document summarizes the key points of control in gene regulation in eukaryotes. It discusses how gene expression is regulated at multiple stages, including DNA packing, transcription, mRNA processing and transport, translation, and protein processing. Regulation can occur through mechanisms like histone modification, DNA methylation, alternative splicing, RNA interference, and protein degradation. The complex gene regulation in eukaryotes allows for specialization of cells and long-term processes, compared to the simpler prokaryotic system.

1. By
KAUSHAL KUMAR SAHU
Assistant Professor (Ad Hoc)
Department of Biotechnology
Govt. Digvijay Autonomous P. G. College
Raj-Nandgaon ( C. G. )

2. Synopsis
• Introduction
• The big question
• Evolution of gene regulation
• Gene regulation in eukaryotes
• Points of control
 Packing/unpacking DNA
 Transcription
 mRNA processing
 mRNA transport
 Translation
 Protein processing
 Protein degradation
• Difference between eukaryotic &
prokaryotic gene expression
• Conclusions
• References

3. Introduction
Gene -Regulation
• Expression of genetic information by eukaryotic cell
is a multi step process, beginning with transcription
of DNA, and ending with a protein that perform a
particular function.
• Gene expression is the process by which information
from a gene is used in the synthesis of a functional
gene product.

4. The Big Question….?
• How are genes turned on & turned off in
eukaryotes ?
• How do cell with the same genes differentiate
to perform completely different, specialized
functions ?

5. Evolution of gene regulation
Eukaryotes
Multicellular
 Evolved to maintain constant internal conditions
while facing changing conditions –Homeostasis
Regulate body as a whole
-Growth and development
-Long term processes
Specialization
-Turn off and on long number of genes

6. GENE REGULATION

7. Points of control
The control of gene expression
can occur at any step in pathway
from gene to functional protein
 Packing/unpacking DNA
 Transcription
 mRNA processing
 mRNA transport
 Translation
 Protein processing
 Protein degradation

8. DNA Packing
• How do you fit
all that DNA into
nucleus ?
 DNA coiling &folding
 Double helix
 Nucleosomes
 Chromatin fibers
 Looped domain

9. Neucleosomes
• “Beads on string ”
 First level of DNA packing
 Histone protein
o 8 protein molecules
o Positively charge amino acid
o Bind tightly to negatively charge DNA

10. DNA packing as gene control
• Degree of packing of DNA regulates transcription
 Tightly wrapped around histone
 No transcription Heterochromatin –Darker DNA [Tightly packed ]
 Genes turned off Euchromatin - Lighter DNA [Loosely packed ]

11. DNA methylation
Methylation of DNA block transcriptional factors
No transcription
- genes turned off
Attachment of methyl
Group to cytosine
Nearly permanent
activation of gene

12. Histone acetylation
Acetylation of histones unwind DNA
 Loosely wrapped around histone
• Enable transcription
• Genes turned on
 Attachment of acetyl group to histone
• conformational change in histone protein
• Transcription factor have easier access
to genes

13. Transcription initiation
Control region on DNA
 Promoter
 Nearby control sequence on DNA
 Binding of RNA polymerase & transcription factor
 “base” rate of transcription
 Enhancer
 Distant control sequence
on DNA
 binding of activator protein
 “enhanced “ (high level) rate of
transcription

14. Model for enhancer action

15. Transcription complex

16. Post - transcriptional control
Alternative RNA splicing
 Variable processing of exons creates a family of protein

17. Regulation of mRNA degradation
Life span of mRNA determines amount of
protein
 mRNA can lost from hours to weeks

19. RNA interference
Small interfering RNAs (siRNA)
1.short segment of RNA (21-28)
(a) bind to mRNA
(b) create section of double-stranded mRNA
(c) “death” tag for mRNA
(i) Triggers degradation of mRNA
2.cause gene “silencing”
(a)post transcriptional control
(b)Turn off gene=no protein produce

20. Action of siRNA

21. Control of translation
Block initiation of translation stage
 Regulatory protein attach to 5’ end of mRNA
(1) Prevent attach of ribosomal subunit & initiator tRNA
(2) Block translation of mRNA to protein

22. Post - translational modification

23. Protein processing and
degradation
Protein processing
 Folding cleaving, adding sugar groups, targeting for
transport
Protein degradation
 Ubiquitin tagging
 Proteasome
degradation

24. Differences between eukaryotic
and prokaryotic gene regulations
• Repetitive DNA
• Coding and non coding gene
• RNA polymerase
• Transcription & translation site

25. Conclusions
• Regulation of gene expression in eukaryote is
complex than prokaryotes and requires many
regulatory, transcriptional and translational factors.
• The regulation can be seen at many stages – genomic
, pre transcriptional, post transcriptional, pre
translational and post translational levels.

26. References
• Cell & molecular biology by-
Gerald Karp
• The cell ,fourth addition by-
Geoffrey M. Cooper
Robert E. Hausman
• Gene expression first edition by-
C.B.Powar
• WWW.wikipidia.com.