<P> Chromatin and its interaction with enzymes has been researched, and a conclusion being made is that it is relevant and an important factor in gene expression . Vincent G. Allfrey, a professor at Rockefeller University, stated that RNA synthesis is related to histone acetylation . The lysine amino acid attached to the end of the histones is positively charged . The acetylation of these tails would make the chromatin ends neutral, allowing for DNA access . </P> <P> When the chromatin decondenses, the DNA is open to entry of molecular machinery . Fluctuations between open and closed chromatin may contribute to the discontinuity of transcription, or transcriptional bursting . Other factors are probably involved, such as the association and dissociation of transcription factor complexes with chromatin . The phenomenon, as opposed to simple probabilistic models of transcription, can account for the high variability in gene expression occurring between cells in isogenic populations </P> <P> During metazoan spermiogenesis, the spermatid's chromatin is remodeled into a more spaced - packaged, widened, almost crystal - like structure . This process is associated with the cessation of transcription and involves nuclear protein exchange . The histones are mostly displaced, and replaced by protamines (small, arginine - rich proteins). It is proposed that in yeast, regions devoid of histones become very fragile after transcription; HMO1 an HMGB protein helps in stabilizing nucleosomes - free chromatin . </P> <P> The packaging of eukaryotic DNA into chromatin presents a barrier to all DNA - based processes that require recruitment of enzymes to their sites of action . To allow the critical cellular process of DNA repair, the chromatin must be remodeled . In eukaryotes, ATP dependent chromatin remodeling complexes and histone - modifying enzymes are two predominant factors employed to accomplish this remodeling process . </P>

How is chromatin organised in the interphase nucleus