1 Chromatin Structure and Function in Neurospora crassa

Eukaryotic DNA is packaged with histones and nonhistone proteins to form a heterogeneous protein-DNA complex called chromatin. Regulation of chromatin structure plays a central role in nearly all DNA-based processes in the nucleus—including transcription, DNA replication, DNA repair, and chromosome segregation. Regulation of chromatin structure is achieved through multiple interrelated mechanisms including modification of DNA and histones, binding of nonhistone proteins, ATP-dependent nucleosome remodeling, and higher-order compaction and folding of the chromatin fiber. These mechanisms work in concert to partition the genome into structurally and functionally distinct chromatin environments. Euchromatin is generally decondensed and transcriptionally active, whereas heterochromatin is highly condensed and transcriptionally silent. Work in the model fungus Neurospora crassa has been of particular importance for elucidating relationships between chromatin structure and function, serving as a model for other fungi and for eukaryotes in general. This chapter summarizes our current understanding of chromatin structure and function in N. crassa.