Tet proteins in the limelight

摘要

During mammalian development, the one-cell zygote gives rise to a multitude of cell types. This remarkable process is controlled by protein machines that interpret the genetic code and regulate the expression of genes, in part by chemically modifying chromatin (DNA-protein complexes). One such modification is the addition of a methyl group at the 5-position of the cyto-sine base in DNA (5mC) - an alteration that serves a crucial role in the epigenetic (or cell-to-cell) inheritance of gene expression during development. However, proteins of the Tet enzyme family can modify this DNA mark further by hydroxylating the methyl group to form 5-hydroxymethylcytosine (5hmC). Five papers4"8, including four in this issue, report on the extent of 5hmC modification across the genome of mouse embryonic stem cells and on the role of Tet proteins in regulating gene expression.