5. Histone modifications and their role in epigenetic regulation
Eukaryotic DNA is organized in a DNA-protein complex called chromatin. A nucleosome core is the basic building block of chromatin and consists of an octamer of small basic proteins named histones. Two loops of DNA (approximately 147 bp) are wrapped around a histone octamer called the histone core. The octamer consists of two copies each of histone proteins H3, H4, H2A, and H2B, each of these is encoded by 10 to 50 intronless copies of the histone gene. The H3/H4 tetramer appears to be more stable in chromatin than the H2A/H2B dimer. A nucleosome array provides an approximately sevenfold DNA condensation. Another histone, H1, binds to the linker DNA region (approximately 80 bp in ...
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