epigenetic&ms pcr inna
TRANSCRIPT
EPIGENETICS & MSP
Kursus Teknik Biologi Molekuler, October 2015
Inna ArmandariDepartment of Histology and Cell Biology Faculty of Medicine, Universitas Gadjah Mada
Epigenetic phenomena
Identical twins
Calico cat
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Epigenetic, Environment, and Disease
Constant interaction between external and internal environments occur via epigenetic process. These will lead to normal development and health maintenance as well as for influencing disease load and resistance.
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Kursus Teknik Biologi Molekuler 2015Kanherkar et al., 2014
Epigenetics vs Genetics
Epigenetic was first coined by Conrad Waddington in 1942
Every cell has identical genome, but the terminal phenotype is not fixed
Therefore, epigenetic serves as a bridge between genotype and phenotype
Various unspecified non-genetic mechanisms influencing phenotype
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Epigenetic
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• Epigenetic comes from Greek :Epi (επί- over, above, outside of ) –genetics
• Epigenetic is heritable changes in gene activity and expression that occur without alteration in DNA sequence
• Epigenome reflects the overall epigenetic state of a cell and refers to global analyses of epigenetic markers across the entire genome.
Epigenetic modifications Epigenetic modifications are crucial for
packaging and interpreting the genome under the influence
They can be considered as the punctuation marks in the genome
They demarcate the start and end of genes; provide structure to the chromosome; lead to genes being expressed (active) or repressed (silent, inactive)
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Epigenetic mechanism
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DNA methylation The covalent addition of a
methyl group at position 5 of cytosine 5-methyl C or CMe
In human & other mammals : occur at cytosine next to guanine, linked by phosphate CpG site
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CpG islands
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Short stretches of CpG-dense DNA promoter regions transcription start site
In human, 60-80% of 28 million CpG dinucleotides are methylated
Cme in a CpG island denotes inactive promoter owing to the condensation of chromatin
Detecting methylated DNA
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Specific technique to detect methylation at CpG island methylation specific (MS)-PCR
MSP principle
DNA methylation and cancer
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Esteller M Hum. Mol. Genet. 2007;16:R50-R59
Histone code Histones are the core protein that
provide structural backbone where DNA is packed into chromatin
Octamer histone consist of two of each of histones H2A, H2B, H3, and H4
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Histone modifications
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Post-translational changes on the histone tails, that are flexible stretches of N or C terminal residues extending from the globular histone octamer
Type of Modifications : •Acetylation•Methylation•Phosphorylation•Ubiquitination
Histone modifications
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Epigenetic state of histone15
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Histone acetylation and gene transcription
RNAs-based mechanism
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Type of post-transcriptional gene modification during which the gene expression is down-regulated or suppressed by Non-coding RNA (ncRNA)
Non-coding RNA (ncRNA) : RNA molecule that is not translated into protein microRNA (miRNA) and small interfering RNAs (siRNA)
microRNA
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Small non-coding RNA molecule (±22 nucleotides) functions in RNA silencing and post-transcriptional regulation of gene expression
bind to complementary sequences on target messenger RNA transcripts (mRNAs) translational repression and gene silencing
miRNA function
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Small interfering (siRNA)
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a class of double stranded RNA molecules (±25 bp) that plays role in RNAi pathway
siRNA functions by causing mRNA to be broken down after transcription no translation
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Inna ArmandariDepartment of Histology and Cell Biology