Heterochromatin: A critical part of the genome

Abstract

Heterochromatin represents highly condensed portions of the genome that are located near centromeres and telomeres of chromosomes. Once thought to be merely junk DNA, heterochromatin is now recognized as an important part of the genome that possesses many functions. Heterochromatin is distinguished from the gene-rich euchromatin by a high concentration of repetitive DNA sequences, including transposons and is marked by specific histone posttranslational modifications and distinct nonhistone chromosomal proteins. Heterochromatin is required for proper chromosome segregation and maintenance of silencing. Loss of heterochromatin leads to the inappropriate activation of genes, including transposable elements, which contribute to genomic instability in diseases such as cancer.