Transcription of chromatin: these are complex times.

Transcription of chromatin-packaged genes involves highly regulated changes in nucleosomal structure that control DNA accessibility. Two systems that facilitate these changes are ATP-dependent chromatin remodeling complexes and enzymatic complexes which control histone acetylation and deacetylation. Recent studies provide insight on the role of these remodeling machines and specific transcription factors in the expression of viral, inducible, and tissue-restricted genes.