title: Accessing the Inaccessible: The Organization, Transcription, Replication, and Repair of Heterochromatin in Plants.
abstract: Eukaryotic genomes often contain large quantities of potentially deleterious sequences, such as transposons. One strategy for mitigating this risk is to package such sequences into so-called constitutive heterochromatin, where the dense chromatin environment is thought to inhibit transcription by excluding transcription factors and RNA polymerase. This type of model makes it tempting to think of heterochromatin as an inert region that is isolated from the rest of the nucleus. Recent work on heterochromatin, however, reveals that it is a dynamic environment. Despite its dense packaging, heterochromatin must remain accessible for a host of processes, including DNA replication and repair, and, paradoxically, transcription. In plants, transcripts produced by specialized RNA polymerases are used to target regions of the genome for silencing via DNA methylation. Thus, the maintenance of heterochromatin requires a careful balancing act of access and exclusion, which is achieved through the action of a host of interrelated pathways.
authors.affiliation: Carnegie Institution for Science, Department of Plant Biology, Stanford, California 94305; email: wfeng@carnegiescience.edu.
authors.forename: Wei
authors.initials: W
authors.lastname: Feng
authors.affiliation: Department of Biology, Indiana University, Bloomington, Indiana 47405; email: michaels@indiana.edu.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Michaels
mesh_terms: D019175:DNA Methylation; D004260:DNA Repair / Q000502:physiology*; D004261:DNA Replication; D006570:Heterochromatin / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D006657:Histones / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D006570:Heterochromatin; D006657:Histones; D012335:RNA, Ribosomal
keywords: DNA methylation; DNA repair; DNA replication; chromatin organization; chromocenters; ribosomal DNA