Abstract:
Chromatin is the complex nucleoprotein structure of DNA wrapped around the
histones. This structure undergoes several hierarchical and distinct organizational states,
aided by not only histones, but also nonhistone proteins and small RNAs, finally resulting
into the compact entity packed into the tiny confines of the nucleus. The higher order
chromatin is a deterrent to the essential cellular processes like transcription, replication and
repair. Hence, there exists a dynamicity wherein based on the signals, the chromatin undergoes decompaction, thereby exposing the DNA for the above mentioned processes.
Once the requirement is met, the chromatin once again compacts (Kouzarides, 2007). This is
probably, the reason for chromatin being considered as a ‘relay platform of different signals’.
However, this dynamicity is not a global phenomena, rather is a local process involving only
certain chromatin territories. The eukaryotic genome is arranged into several chromatin
territories interspersed with empty spaces, leading to a three dimensional fluid
representation of chromatin. Thus, any cellular process is an event recognized by specific
chromatin territories (Meaburn and Misteli, 2007) which interact with other regions if
essential by processes called gene looping and thereby lead to gene expression.
