Gene expression Flashcards
Type of cells in multi cellular organism ?.
1- housekeeping
General
both brain and
liver cells transcribe genes that code for enzymes and other molecules essential to the survival of all cells
2- non general
liver cells transcribe liver-specific proteins,
brain cells transcribe brain-specific proteins
difference in the protein production pattern is due to …..?.
differential transcription
What is the major control point for the
Gene Expression
regulation of gene expression in eukaryotic cells
Transcriptional control
Mechanism of Regulation of Gene Expression?.
1- Remodling of chromatin
2- transcriptional control
How many proteins are involved in initiating transcription?
1600 TF
Does all the regulation proline bind directly to
DNA ?
Many (but not all)
The location of enhancer ?
Intron encoding region
only in specific cell types
Meaning of activator proteins and Repressors?
Both regulatory proteins
Repressors act to turn
off transcription
activator stimulate transcription
Mechanism of Repressors to turn of the transcription?
Competing with activators
masking activator activity
direct negative interaction
on the transcription complex
assembled at the promoter (silencers)
Mechanism of proteins to binding with DNA?
Motifs For Protein–DNA Interactions ?
Proteins that directly bind DNA have a DNA-binding
region whose protein surface is partially “complementary” to the surface features of the DNA recognition site
✓ Helix-turn-helix Regulate genes involved in development ✓ Leucine (basic) zipper Cell division genes ✓ Zinc finger Steroid hormone receptors ✓ Helix-loop-helix Immune sys genes
Diners proteins increases or decrease or no change in regulatory options ?
increases
Ways Regulation Of Activity Of Gene Regulatory Proteins?
- Protein synthesis
- Ligand binding
- Protein phosphorylation
- Addition of a second subunit
- Unmasking
- Stimulation of nuclear entry
- Release from membrane
RNAs Involved In Regulating Gene Expression ?.
microRNAs
Negatively regulate gene expression through
sequence-specific base-pairing with mRNA targets
siRNAs
regulate activity of transposons
few protein coding genes
viral infection
piRNAs
development of germ cells
(sperm in mammals)
Slide 20
Example of regions are constitutively silenced in chromatin ?
telomeres
What is the chromatin loop
chromatin loops ‘isolate’ the ‘active’ chromatin within
• It is proposed that the base of
a chromatin loop functions as an insulator element –
protein binding
Regulation of Chromatin Assembly and Structure
Involves:
- ATP-dependent chromatin remodelling
* Histone modifications
Meaning of Epigenetic?
Stably heritable phenotype……….from change in the chromosome without alteration in DNA sequence
Function of Remodeling proteins
Disaggregate of nucleosome
Why we need energy of ATP
In Chromatin Re-modelling ?.
ATP
hydrolysis to bind DNA and move histone octomers of nucleosomes
List of Modification Of Histones
.?
Acetylation lysine, arginine Methylation.lysine (3), arginine (2)
Phosphorylation serine, threonine Ubiquitination lysine
ADP-ribosylation
Glycosylation
Histone Acetylation reversible ?
acetylate
(histone acetyltransferases; HATs),
or deacetylate (histone deacetylases; HDACs)
Which base and carbine does the methyl add to ?
Cytosine
Carbon 5
functions in mammals of DNA Methylation?
Control of gene expression
• Cellular differentiation and development (programs
of gene expression)
• Preservation of chromosomal integrity
• X-chromosome inactivation
• Implicated in brain function and development of the
immune system
• Alterations in genomic patterns contribute to human cancers
Example of m mutation of MeCBP2
X-linked Rett Syndrome,
a progressive neuromuscular
disorder
Linkage between DNA methylation and transcriptional
repression by ?
histone deacetylation
Genomic Imprinting meaning ?
Physical basis is that the gene from one parent is
“silenced” by methylation
Phenomenon in which the expression of the gene determines by whether you inherited from father or mother ?
When genes become all demethylated ?
Grem line cell
Where Igf2 and H19 works ?
Igf2 father
H19 mother
Example of imprinting genomic ?
Igf2 ,H19
Example of Disease may result if:
The active parental copy is affected by
mutation
prader-willi and angelman syndromes)
And beck with wiedemann syndrome
Method of Implications For Inherited Disease ?
Mutation occurs in genes controlling
imprinting
Imprinting control region if it is become methylated make two imprinting gene
If it is become unmethylated it will one imprinting gene
In early embryo From pre-gastrulation onwards the extent of
methylation varies?
✓ Somatic cell lineages (heavy methylation)
✓ Trophoblast-derived lineages (giving rise to placenta,
yolk sac – less methylated)
✓ Primordial gene cells (largely unmethylated)
Mechanism of X Chromosome Inactivation?
Xist gene on X chromosome
Xist transcribe to interference RNA
RNA binds to the same X chromosome
Methylation and Huston deacetylation attract chromosome proteins
Inactivation X chromosome
What is Barr body ?
Condensed inactive X chromosome.
