Introduction to theme "Chromatin, epigenetics, and transcription".

Transcriptional regulation in eukaryotes depends on a complex network of interactions between RNA polymerases and a host of transcription factors and coregulators that control their activity during transcription initiation and elongation. Among these are an enormous variety of enzymes and proteins that modulate chromatin structure via changes in DNA methylation, histone modifications, and nucleosome location. This volume of the Annual Review of Biochemistry contains a set of four reviews addressing the interplay between mechanisms that regulate DNA methylation, chromatin structure, and transcription.