Difference between revisions of "KSH 0611 Review Epigenetic modifications regulate gene expression"

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imported>Seung-hoon Kim
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<li>Chemical modification to the cytosine residues of DNA (DNA methylation)</li>
 
<li>Chemical modification to the cytosine residues of DNA (DNA methylation)</li>
 
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<p>DNA methylation usually occurs in cytosine followed by guanine (CpG) by DNA methyltransferase</p>
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<p>Most CpG motifs (Repetitive short pattern in DNA sequence or Protein sequence) are located near promoter regions.<sup>1)</sup></p>
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<p>Promoter is a region of DNA that initiates transcription of a&nbsp;particular gene</p>
  
 
<p>​<img src="http://www.ks.uiuc.edu/Research/methylation/dna_mdna.png" />(http://www.ks.uiuc.edu/Research/methylation/dna_mdna.png)</p>
 
<p>​<img src="http://www.ks.uiuc.edu/Research/methylation/dna_mdna.png" />(http://www.ks.uiuc.edu/Research/methylation/dna_mdna.png)</p>
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<h2>Reference</h2>
  
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<p>1)&nbsp;Bird, Adrian P. &quot;CpG-rich islands and the function of DNA methylation.&quot;&nbsp;<em>Nature</em>321.6067 (1985): 209-213.</p>

Revision as of 13:55, 11 June 2016

 Epigenetics

Definition : Heritable changes in gene activity and expression that occur without alteration in DNA sequence

Different cells control switching on and off in different genes

Two well-known epigenetic modifications

  • Chemical modification to the cytosine residues of DNA (DNA methylation)

DNA methylation usually occurs in cytosine followed by guanine (CpG) by DNA methyltransferase

Most CpG motifs (Repetitive short pattern in DNA sequence or Protein sequence) are located near promoter regions.1)

Promoter is a region of DNA that initiates transcription of a particular gene

​(dna_mdna.png)

  • Histone modification

Why is it important ? >>> Epigenetic  modifications regulate gene activity and expression during development and differentiation, or in response to environmental stimuli

Epigenetics is considered a bridge between genotype and phenotype

Explain how cells carrying identical DNA differentiate into different cell types >>> Epigenetics

Epigenome - global analyses of epigenetic markers across the entire genome

Chromatin - Histone protein / DNA complex in eukaryotic cells

Basic Unit - nucleosome - 146 bp of DNA wrapped around an octamer of the four core histones (H2A, H2B, H3 and H4)

  1. Euchromatin - transcriptionally active state - the region where DNA is accessible due to the relaxed state of nucleosome arrangement
  2. Heterochromatin - transcriptionally inactive state - the area where DNA is packed into highly condensed forms that are inaccessible to transcription factors

How to regulate Protein Synthesis - Epigenetic inheritance controls the amount of the transcribed mRNA. Thus, protein production is regulated.

Ex) Alcohol dehydrogenase (ADH) breaks down alcohol in liver cells.

We could increase the mRNA of ADH  and then make ADH more than usual when we drink much 

Only 2 % of human genome encodes protein and the other 98% controls gene expression by epigenetic mechanism.

 

Reference

1) Bird, Adrian P. "CpG-rich islands and the function of DNA methylation." Nature321.6067 (1985): 209-213.

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