Lecture 27 Chromatin & Epigenetics

Lecture 27 Chromatin & Epigenetics - Chromatin and...

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Chromatin and Epigenetics Dr. Matera 27 Mar 2009 Model of histone octamer core (A). When octamer is  bound to DNA (B), it is called a ‘nucleosome.’
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Bacterial DNA is condensed in the cell 400x compaction of DNA in ‘nucleoid’
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Eukaryotic DNA is  highly  condensed 10,000x compaction ratio in metaphase DNA + associated proteins = ‘chromatin’ Chromatin not compacted as highly during interphase Metaphase vs. Interphase
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11 nm wide “Beads-on-a-string” 30 nm wide “Zigzag” or “Solenoid” Gentle isolation of interphase chromatin reveals 30 nm and 11 nm fibers Interphase Chromatin What are the beads??
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Properties of histones? Nucleosome experiment
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The N-terminal “tails” are lysine rich. The C-terminal domains share a common “histone fold” structure. Histones: “basic” building blocks The histone fold, illustrated by  H2A ( red ) and H2B ( gold )
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N-terminal tails not structured in crystal – importance long underappreciated
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Histone tails extremely important for regulating gene expression Covalent modification of tails and the “histone code” N-terminal tails
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Deciphering full histone code will continue to be a subject of intense investigation over the next decade The Histone Code 
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H1 helps compact DNA even further by charge shielding and possibly by altering the path of
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Lecture 27 Chromatin & Epigenetics - Chromatin and...

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