1. REGULATION OF GENE
EXPRESSION IN
EUKARYOTES
SUBMITTED TO : SUBMITTED BY
Ms: SHRADDHA GOSWAMI BRAJBALA MISHRA
BIOTECHNOLOGY DEPARTMENT MSC II SEM

2. Contents
 Introduction of Regulation
of Gene Expression in
Eukaryotes .
 Cis-acting elements ,
Chromatin Organization &
regulation at the level of
processing of transcripts.
 RNA-Editing ,Gene
Alteration,DNA Methylation
,Regulation of gene
expresson by hormone &
Regulation of gene at
translational level.

3. INTRODUCTION
 Objectives
 Know the different levels at which gene
expression is regulated in eukaryotes,
and understand the principles of
regulation at each level.
 Understand the functional difference
between promoters and enhancers.
 Understand the basics of tissue-specific
gene regulation.

4. Eukaryotic Gene Expression
 Gene Expression :-
 “Gene expression" covers the entire process
from transcription through protein synthesis
 Eukaryotes have more complex means to regulate
gene expression, because they have compartments
(e.g., nucleus) within cells, and often multicellular
structures that require differentiation of cells.
.

5. Eukaryotic Gene Regulation
 Genome (amplification or
rearrangement of DNA segments,
chromatin remodeling:
decondensation/ condensation
and DNA methylation).
 Transcription.
 Processing (and nuclear export)
of RNA.
 Translation (and targeting) of
protein.
 Posttranslational events (folding
and assembly, cleavage, chemical
group modifications and organelle
import/secretion).
 Degradation of mRNA and
proteins

6.  Proximal elements of promoter
 in prokaryote: -35 region
 in eukaryote: CAAT-box, GC-box
UPE: upstream promoter element
UAS: upstream activating sequence
(2) Terminator
A DNA sequence just downstream of the coding
segment of a gene, which is recognized by RNA
polymerase as a signal to stop transcription.

7. (3) Enhancer
A regulatory DNA sequence that greatly
enhances the transcription of a gene.
(4) Silencer
A DNA sequence that helps to reduce
or shut off the expression of a nearby gene.

8. Chromatin Organization
Two forms of chromatin
o Euchromatin – A lesser coiled
transcriptionally active region which can be
easily accessed by the RNA polymerase
o Heterochromatin – A highly condensed
transcriptionally inactive region. The genes
in this region cannot be accessed by the
RNA polymerases for active transcription

9. Different
chromatin remodeling complexes
disrupt
and reform nucleosomes. The same
complex might catalyze both
reactions. The DNA-binding
proteins could be involved in gene
expression, DNA replication, or
DNA repair.

10. Chromatin Structure

11. Transcription Regulation
Genes are nearly always transcribed
individually3 RNA Polymerases occur, requiring
multiple proteins to initiate transcription
Typical eukaryotic promoter: recognition
sequence + TATA box + transcription factors
-> RNA Polymerase II attachment ->
transcription

13. Transcription Regulation
 RNA polymerase interacts w/promoter,
regulator sequences, & enhancer
sequences to begin transcription
– Regulator proteins bind to regulator sequences
to activate transcription
 Found prior to promoter
– Enhancer sequences bind activator proteins
 Typically far from the gene
 Silencer sequences stop transcription if
they bind with repressor proteins

15. Transcription Regulation
Con’t
 If eukaryotic genes
are typically
‘alone’, to regulate
expression of
several.
 Conserve regulatory
sequences!

16. RNA Editing
 RNA editing is a molecular process through which some cells
can make discrete changes to specific nucleotide
sequences within a RNA molecule after it has been generated
by RNA polymerase
 RNA editing is relatively rare, and common forms of RNA
processing (e.g. splicing, 5'-capping and 3'-polyadenylation)
are not usually included as editing. Editing events may include
the insertion, deletion, and base substitution of nucleotides
within the edited RNA molecule.

17.  RNA editing occurs in the cell nucleus
and cytosol, as well as
within mitochondria and plastids.
 RNA editing has been observed in
some tRNA, rRNA, mRNA and miRNA
molecules of eukaryotes and
their viruses, but has not been seen
in prokaryotes

18. RNA –editing Funtions

19. RNA –Editing Process

20. Gene Alteration
 chromosomes may alter abnormally - this is
said to be a: mutation. It causes
miscoded mRNA
 Genetic engineering alters the genetic
makeup of an organism using techniques
that remove heritable material or that
introduce DNA prepared outside the
organism either directly into the host or into
a cell that is then fused or hybridized with
the host

22. DNA-Methylation
DNA methylation involves the addition of
a methyl group to the 5 position of the
cytosine pyrimidine ring or the number
6 nitrogen of the adenine purine ring
In addition, DNA methylation suppresses
the expression of viral genes and other
deleterious elements that have been
incorporated into the genome of the
host over time.

23. DNA -Methylation
 The attachment of methyl groups (-CH3) to DNA
bases after synthesis
 Inactive DNA is generally highly methylated
compared to DNA that is actively transcribed
– The same genes in different tissues are more
heavily methylated in cells where they are not
expressed
– Demethylating inactive genes can turn them on
 May determine long term inactivation of genes
 Methylation patterns are passed on, preserving a
record of embryonic development
– May account for genomic imprinting in mammals
– Methylation permanantly turns off either the
maternal or paternal allele of some genes

24. The role of methylation in
Gene Expression
 role in repressing gene
expression, perhaps by
blocking the promoters at
which
activatingtranscription
factors should bind
 proper DNA methylation
is essential for cell
differentiation and
embryonic development.

25. Regulation of gene
expression by hormone
 Hormone affect th eregulation of gene
expression in one of two ways.
 Steroid Hormones : A group of
hydrophobic hormones that are
derivatives of cholesterol.The effect of
steriod hormones in eukaryotic
regulatory proteins by direct
interaction with molecular signals.

26. Mechanism of hormones
in gene regulation.
Steroid hormones enters,its target cells
&combine with a receptor protein
The hormones/receptor complex bind to a
hormones response element in the DNA
The bound complex stimulates transcription

27. The mRNA is translated into proteins .
Regulaation of gene expression by steriod
hormones
The hormones interacts with a receptor
inside its target cells & resulting complex
moves into the nucleus , where it activate
the transcription of particular gene

28. Regulation of gene by
steroid hormone

29. Regulation of gene expression
at Translational level.
 1. Translation Control
 Blocking mRNA Attachment to
Ribosomes
 2. Regulation of Protein Processing
 Protein Modification

30.  Inititation factors are subjected to
phosphorylation by a no. of protein
kinases.
 Some protein binds directly to mRNA
& Act as translational repressor, many
of them binding at specific sites in the
3’ un translated region .

31. 7 Gene
6 protein
processing &
degradation
Regulation
1 & 2. transcription
- DNA packing
- transcription factors
3 & 4. post-transcription
5 - mRNA processing
initiation 4 - splicing
of - 5’ cap & poly-A tail
mRNA
translation processing
- breakdown by siRNA
5. translation
- block start of
2
1 translation
initiation of
transcriptio 6 & 7. post-translation
n - protein processing
- protein degradation
mRNA
mRNA 4 protection
3 splicing

32. Discussion
 Regulation of Gene Expreesion in Eukaryotes :Any
of the processes by which nuclear, cytoplasmic, or
intercellular factors influence the differential control
of gene action during the developmental stages of
an organism.

33. THANK YOU