Biochemical Mediators and Mechanisms Involved in Chromatin Conformational Remodeling through the Cell Cycle.

ABSTRACT

Chromatin undergoes structural remodeling through the cell-cycle stages. Remodeling of the chromatin structure is extremely important for events occurring during these stages. The five major levels of structural organization, from the double-strand structure to the metaphase chromosomes are possible due to specific factors and mechanisms that function in synchrony. The mitotic promoting factors, the "structural maintenance of chromosomes" proteins, and proteins associated with cytoskeletal and nucleoskeletal elements have specific roles in structural modeling and functioning of DNA. It is of interest that the DNA decondensation cycle opposes the DNA condensation cycle. However, it is not clear if the factors and mechanisms involved in the DNA decondensation cycle are exactly opposite to the DNA condensation cycle. Also interesting is that chromosome-specific chromatin is positioned in the interphase nucleus in specific "territories" or "niches," a phenomenon similar to the exactly positioned genes at specific locations on a fully condensed chromosome. We review the factors and mechanisms in remodeling chromatin, maintaining structural integrity at each organizational level, and impact of this structural remodeling on functions of the genetic material.