Chromatin in Eukaryotic Regulation

In eukaryotes, the tight or loose packaging of the genes in chromatin (DNA plus specific proteins) can control whether the genes can be expressed to form their encoded product. Chromatin is usually not "permissive" but it can be modified in specific areas to open it up for transcription of the genes. Chromatin is opened by remodeling complexes. Nucleosomes, eight histone molecules plus associate DNA of about 140 nucleotides' length, can be "closed" by removing acetyl groups on the tails of the histones, or opened by placing acetyl groups there. Placement of acetyl or methyl groups on a specific histone can have opposing effects or additive effects on gene expression. The gene expression effect of histone modification placements is called the histone code. DNA itself can be methylation and that also regulates gene expression, generally to turn off the gene.

Last Updated: January 17, 2014