Chromatin Remodeling

 

 

 The packaging of chromosomal DNA by nucleosomes condenses and organizes the genome, but occludes many regulatory DNA elements.This packaging of DNA into nucleosomes and higher order structure is generally inhibitory to all kind of DNA dependent processes. To overcome DNA sequence accessibility problems, cells have developed mechanisms to open higher order structures of chromatin and to disrupt nucleosomes allowing the binding of sequence specific regulators.

 

            Chromatin remodeling is the enzyme­ assisted process to facilitate access of nucleosomal DNA by  remodeling the structure, composition and positioning of nucleosomes. It is the dynamic modification of  chromatin architecture to allow access of condensed genomic DNA to the regulatory transcription machinery proteins, and thereby control gene expression.

 

            The  Chromatin remodelling involves two type of modifications first one is covalent histone modification in this Specific protein complexes, known as Histone- Modifieng complexes catalyze addition or removal of  various chemical  elements on  histones. Another one is ATP ­ dependent chromatin remodeling which involves different remodeler families. Remodelers use the

energy of ATP hydrolysis to change the packaging state of chromatin by moving, ejecting, or restructuring the nucleosome

 

         Many of the chromosomal processes like . Chromatin Assembly, Dosage Compensation, .  DNA Replication, Transcription, DNA Repair, Chromosome Segregation depends on Chromatin remodeling.

            A research was conducted on Drosophila melanogaster  which clearly explain the role of  ISWI chromatin remodeling factor  in chromatin  compaction by loading  H1 histone into the chromatin. It was concluded by using polyclonal antibody specific for H1. It reveals role of ISWI   regulation of gene expression.

 

          In Arabidopsis thaliana the Trimethylation on H3K4  which is a covalent histone modification helps  in  Systemic Acquired Resistance during plant stress which can activate the defence genes for the subsequent infection by the pathogen. In this research the BTH (acibenzolar S-methyl)  Analog of plant hormone salicylic acid as an elicitor.

 

KEY WORDS: Chromatin Remodeling, chromosome, DNA, hostone, nucleosome

 

REFERENCES:

1.Allfrey VG, Faulkner R, Mirsky AE,1964.,. Acetylation and methylation of histones and their possible                role in the regulation of RNA synthesis. Proc Natl Acad Sci USA ; 51:786-794.

 2. Corona DF, Tamkun JW. 2004., Multiple roles for ISWI in transcription, chromosome organization and DNA replication. Biochim. Biophys. Acta 1677:113–19

3.Corona DFV, Siriaco G, Armstrong JA, Snarskaya N, McClymont SA, et al. (2007) ISWI regulates higher-order chromatin structure and histone H1 assembly in vivo. PLoS Biol 5(9): e232. doi:10.1371/journal.pbio.0050232

4. Jaskiewicz M ,  Conrath U , Peterha¨nsel C.2011.,Chromatin modification acts as a memory for systemic acquired resistance in the plant stress response, 50–55. doi:10.1038/embor.2010.186.