Gene expression in eukaryotes involves two main steps: transcription and translation. Regulation of eukaryotic gene expression depends on regulatory elements like promoters and enhancers as well as transcription factors. Gene expression can be regulated at multiple steps, including chromatin modification, transcription, RNA processing, mRNA degradation, translation, and protein degradation. Chromatin modification like DNA methylation and histone acetylation can regulate unpacking of DNA and transcription. Transcription factors activate or repress transcription by binding to regulatory elements. Post-transcriptional processes like RNA processing and degradation can also influence gene expression levels.

1. GENE EXPRESSION AND REGULATION
IN EUKARYOTES
ANILA SAJJAD
MBS-163010

2. Gene expression is the process by which information from a gene
is used in the synthesis of a functional gene product
Gene expression is carried out in 2 steps:
1. Transcription
2. Translation
Regulation of eukaryotic gene expression is dependent on 2
factors
1. Regulatory elements (Promoters & Enhancers)
2. Transcription factors

3. Control of Gene Expression
 What are the steps from chromosome
to functional protein?
 Unpacking →Transcription →
mRNA processing → export from
the nucleus → translation → protein
modification
 ANY of these steps can be regulated
in eukaryotes

4. Chromatin modification
 DNA methylation; the addition of methyl groups to DNA
 essential for inactivation of the DNA
• Inactive genes in a cell are methylated
• Packs DNA closer together and reduces transcription
• Transcriptional Silencing
 So demethylate DNA to unpack from heterochromatin to
euchromatin
 Histone acetylation is the attachment of an acetyl group to
histone proteins
 Acetylation of histone tail promotes loosening of
chromatin

5. Chromatin changes
Transcription
RNA Processing
mRNA
Degadation
Translation
Protein processing
& degradation

6. Transcriptional Control
 Transcription factors that are ACTIVTORS boost a gene’s
 transcription. REPRESSORS decrease transcription
 Group of transcription factors binding sites---- ENHANCERS
 and SILENCERS can turn a gene on/off in specific body parts
 Transcription factors allow RNA pol to find the promoter
region association between transcriptional factors and
enhance. promoter region regulates gene expression

7. Chromatin changes
Transcription
RNA Processing
mRNA
Degadation
Translation
Protein processing
& degradation

8. Post-Transcriptional Control
Four main steps:
1. RNA capping
2. Poly A tail
3. Splicing
4. Alternative
Splicing

9. Post-transcriptional control
 Regulation of RNA processing
 Regulation of mRNA degradation
o Can last from hours to weeks
 Regulation of translation
o initiation sequence can be blocked

10. Chromatin changes
Transcription
RNA Processing
mRNA
Degradation
Translation
Protein processing
& degradation

11. Protein Degradation
Post-translational control

12. References:
1. Amaral PP, Dinger ME, Mercer TR, Mattick JS (March 2008). "The
eukaryotic genome as an RNA machine". Science. 319 (5871):1787–9
2. Hegde RS, Kang SW (July 2008). "The concept of translocational regulation“
3. Jeremy M. Berg, John L. Tymoczko, Lubert Stryer ; Web content by
Neil D. Clarke (2002). "3. Protein Structure and Function“
4. Veitia RA (November 2008). "One thousand and one ways of
making functionally similar transcriptional enhancers". BioEssays.
30 (11–12): 1052–7
5. Bird A (2002). "DNA methylation patterns and epigenetic memory".
Genes Dev. 16 (1): 6–21.