Chromatin-based silencing mechanisms.
Eukaryotic genomes are organized into regions of transcriptionally active euchromatin and transcriptionally inactive heterochromatin. In plant genomes, heterochromatin is marked by methylation of cytosine and methylation of histone H3 at lysine 9. Heterochromatin formation is targeted to transposons as a means of defending the host genome against the deleterious effects of these sequences. Heterochromatin is directed to transposon sequences by transposon-derived aberrant RNA species and functions to prevent unwanted transcription and movement. Formation of heterochromatin at rRNA-encoding genes and centromere-associated repeats might also involve an RNA-based mechanism that is designed to stabilize these potentially labile structures.
Bender
Judith
J
Department of Biochemistry and Molecular Biology, John Hopkins University, Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, USA. jbender@mail.jhmi.edu
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation; D004251:DNA Transposable Elements; D020868:Gene Silencing; D020459:Genes, rRNA; D018745:Genome, Plant; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D008957:Models, Genetic; D010944:Plants / Q000235:genetics* / Q000378:metabolism; D012330:RNA, Double-Stranded / Q000378:metabolism
D004251:DNA Transposable Elements; D006570:Heterochromatin; D006657:Histones; D012330:RNA, Double-Stranded