Regulation of gene expression in eukaryotes
Regulation of gene expression in eukaryotes
Regulation of gene expression in eukaryotes
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Control factors cont<strong>in</strong>ued:<br />
3) DNA methylation (add methyl to C)<br />
• Occurs at 5’ position, usually <strong>in</strong> CG doublets<br />
• 5’- m CpG-3’<br />
– Transcriptionally active <strong>gene</strong>s possess<br />
significantly lower levels <strong>of</strong> methylated DNA<br />
than <strong>in</strong>active <strong>gene</strong>s.<br />
• A <strong>gene</strong> for methylation is essential for development <strong>in</strong><br />
mice (turn<strong>in</strong>g <strong>of</strong>f a <strong>gene</strong> also can be important).<br />
• Methylation results <strong>in</strong> a human disease called fragile<br />
X syndrome; FMR-1 <strong>gene</strong> is silenced by methylation.<br />
Control factors cont<strong>in</strong>ued:<br />
4) Chromat<strong>in</strong> conformation (remodell<strong>in</strong>g)<br />
a. Antirepressors & nucleosome position<strong>in</strong>g.<br />
b. Histone acetylation – (acetyl groups on lys<strong>in</strong>es),<br />
histone acetyltransferase enzyme catalyzes the<br />
addition <strong>of</strong> lys<strong>in</strong>e, targeted to <strong>gene</strong>s by specific<br />
TFs.<br />
c. Heterochromat<strong>in</strong> – highly condensed,<br />
transcriptionally <strong>in</strong>ert (<strong>of</strong>f).<br />
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