The inheritance and maintenance new and old synthesize of DNA b can be explain by semiconservative model. But how is the inheritance of epigenetic traits—modifications of chromatin proteins (histones) and DNA that do not alterthe sequence—affected by dynamic changes in chromatin organization during eukaryotic cell division?
Recently study (Xu et al.) explore how parental (old) and newly synthesized histones associate after replication. The basic unit of chromatin, the nucleosome, has a core particle of eight histones—two pairs of histone H3-H4 as a tetramer flanked by two dimers of histone H2A-H2B. Histones can be present in distinct forms or variants, and they may harbor specific posttranslational modifications that can define a given epigenome ( 1, 3). How do these particular markings sustain passage through replication? An attractive hypothesis has been a semiconservative mechanism in which parental histones are combined with newly synthesized histones within the same core nucleosome. The presence of parental information as a template to reproduce the same marks on new histones provides a convenient means to ensure accurate reproduction of the initial marking at the same place. But can parental and new histones mix?
Histones H2A-H2B readily exchange as dimers, but H3-H4 tetramers are thought not to split. However, newly synthesized H3 and H4 can exist as dimers when associated with histone chaperones. By their study that have 3 possibility of model of the Histone inheritance. First with H3-H4 only new tetramer, second with mixed H3-H4 tetramer and third with only old tetramer.
Future work will investigate how the choice between histone splitting and nonsplitting is made within a cell and
whether this is regulated during cellular life or during development.
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