Epigenetic phenomena in filamentous fungi: useful paradigms or repeat-induced confusion?
Epigenetic mechanisms can serve as genome defense systems. In haploid nuclei of special sexual cells of fungi, such as Neurospora and Ascobolus, duplicated genes are silenced by hypermutation, DNA methylation, or both. In some cases, DNA introduced into the genome of Neurospora cells by transformation can also inhibit homologous genes by a silencing mechanism that does not involve DNA pairing or methylation and appears to be post-transcriptional. Transforming DNA can also trigger de novo methylation in vegetative cells, which then causes transcriptional silencing. The rules governing silencing in vegetative cells of fungi are undefined, but repeated sequences seem particularly susceptible to these processes. Thus, fungi exhibit both repeat-induced and repeat-associated silencing mechanisms. Additionally, some native genes depend on homologous pairing in the diplophase for proper regulation. Together, these processes should limit the proliferation of transposable elements and serve to preserve the overall structure of the genome.
Selker
E U
EU
Institute of Molecular Biology, University of Oregon, Eugene 97403, USA. selker@molbio.uoregon.edu
D000818:Animals; D001203:Ascomycota / Q000235:genetics* / Q000254:growth & development; D019175:DNA Methylation; D004330:Drosophila / Q000235:genetics; D005656:Fungal Proteins; D015966:Gene Expression Regulation, Fungal; D015321:Gene Rearrangement; D009154:Mutation; D009491:Neurospora / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics
C104110:ASM-1 protein, Neurospora crassa; D005656:Fungal Proteins; D014157:Transcription Factors