Search results
Results from the WOW.Com Content Network
The nucleosome is the fundamental subunit of chromatin. Each nucleosome is composed of a little less than two turns of DNA wrapped around a set of eight proteins called histones, which are known as a histone octamer. Each histone octamer is composed of two copies each of the histone proteins H2A, H2B, H3, and H4.
Histones are responsible for maintaining the shape and structure of a nucleosome. One chromatin molecule is composed of at least one of each core histones per 100 base pairs of DNA. [2] There are five families of histones known to date; these histones are termed H1/H5, H2A, H2B, H3, and H4. [3]
The (H3-H4) 2 tetramer is wrapped with DNA around it as a first step of nucleosome formation. Then two H2A-H2B dimers are connected to the DNA-(H3-H4) 2 complex to form a nucleosome. [8] Each of the four core histones, in addition to their histone-fold domains, also contain flexible, unstructured extensions called histone “tails”. [9]
In molecular biology, linker DNA is double-stranded DNA (38-53 base pairs long) in between two nucleosome cores that, in association with histone H1, holds the cores together. Linker DNA is seen as the string in the "beads and string model", which is made by using an ionic solution on the chromatin. Linker DNA connects to histone H1 and histone ...
The region occupied by a chromosome is called a chromosome territory (CT). [43] Among eukaryotes, CTs have several common properties. First, although chromosomal locations are not the same across cells within a population, there is some preference among individual chromosomes for particular regions.
In eukaryotes, this structure involves DNA binding to a complex of small basic proteins called histones. In prokaryotes , multiple types of proteins are involved. [ 8 ] [ 9 ] The histones form a disk-shaped complex called a nucleosome , which contains two complete turns of double-stranded DNA wrapped around its surface.
[2] [13] In eukaryotic cells, DNA is associated with about an equal mass of histone proteins in a highly condensed nucleoprotein complex called chromatin . [ 14 ] Deoxyribonucleoproteins in this kind of complex interact to generate a multiprotein regulatory complex in which the intervening DNA is looped or wound.
Like PARPs 2 and 3, the catalytic activity of PARP-1 is activated by discontinuous DNA fragments, DNA fragments with single-stranded breaks. PARP-1 binds histones near the axis where DNA enters and exits the nucleosome and additionally interacts with numerous chromatin-associated proteins which allow for indirect association with chromatin. [ 30 ]