Chromatin
Chromatin is comprised of histones and DNA: 147 base pairs of DNA wraps around the 8 core histones to form the basic chromatin unit, the nucleosome. The function of chromatin is to efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence. Packaging DNA into chromatin allows for mitosis and meiosis, prevents chromosome breakage and controls gene expression and DNA replication. Find out more about the structure of chromatin and the methods used to investigate chromatin accessibility and interactions.
The genome is efficiently packaged into the nucleus. DNA is wrapped around histones to form a nucleosome, comprised of 147 base pairs of DNA and eight-core histone proteins. Nucleosomes are strung together like beads on a string and packaged into higher-order chromatin architecture (Figure 1). DNA that is tightly bound in nucleosomes or compacted into higher order heterochromatin is inaccessible, preventing the binding of transcription factors, transcriptional machinery, and other DNA binding proteins, resulting in gene silencing. Meanwhile “linker” DNA and open euchromatin architecture are accessible to binding, allowing for active gene transcription. Chromatin is actively and dynamically remodeled to alter gene expression and cellular programming, for example, during different developmental stages or in response to particular stimuli. Large genomic regions may be silenced or activated, or nucleosomes may be unraveled to access specific genes and DNA sequences. Examining the chromatin structure and nucleosome positioning reveals epigenetic programs and mechanisms involved in specific cellular processes and disease states.DNA that is tightly bound in nucleosomes or compacted into higher-order heterochromatin is inaccessible, preventing the binding of transcription factors, transcriptional machinery, and other DNA-binding proteins, resulting in gene silencing. Meanwhile “linker” DNA and open euchromatin architecture are accessible to binding, allowing for active gene transcription. Chromatin is actively and dynamically remodeled to alter gene expression and cellular programming, for example, during different developmental stages or in response to particular stimuli. Large genomic regions may be silenced or activated, or nucleosomes may be unraveled to access specific genes and DNA sequences. Examining the chromatin structure and nucleosome positioning reveals epigenetic programs and mechanisms involved in specific cellular processes and disease states.
Figure 1. Chromatin structure. DNA winds around nucleosomes to form chromatin fiber and then chromosomes.
Source:Abcam