title: Direct interaction between DNA methyltransferase DIM-2 and HP1 is required for DNA methylation in Neurospora crassa.
abstract: DNA methylation is involved in gene silencing and genomic stability in mammals, plants, and fungi. Genetics studies of Neurospora crassa have revealed that a DNA methyltransferase (DIM-2), a histone H3K9 methyltransferase (DIM-5), and heterochromatin protein 1 (HP1) are required for DNA methylation. We explored the interrelationships of these components of the methylation machinery. A yeast two-hybrid screen revealed that HP1 interacts with DIM-2. We confirmed the interaction in vivo and demonstrated that it involves a pair of PXVXL-related motifs in the N-terminal region of DIM-2 and the chromo shadow domain of HP1. Both regions are essential for proper DNA methylation. We also determined that DIM-2 and HP1 form a stable complex independently of the trimethylation of histone H3K9, although the association of DIM-2 with its substrate sequences depends on trimethyl-H3K9. The DIM-2/HP1 complex does not include DIM-5. We conclude that DNA methylation in Neurospora is largely or exclusively the result of a unidirectional pathway in which DIM-5 methylates histone H3K9 and then the DIM-2/HP1 complex recognizes the resulting trimethyl-H3K9 mark via the chromo domain of HP1.
authors.affiliation: Institute of Molecular Biology, University of Oregon, Eugene, OR 97403-1229, USA.
authors.forename: Shinji
authors.initials: S
authors.lastname: Honda
authors.forename: Eric U
authors.initials: EU
authors.lastname: Selker
mesh_terms: D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000032:analysis / Q000378:metabolism*; D019175:DNA Methylation; D015254:DNA Modification Methylases / Q000032:analysis / Q000378:metabolism*; D005656:Fungal Proteins / Q000032:analysis / Q000378:metabolism*; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism; D009492:Neurospora crassa / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D011496:Protein Methyltransferases; D020798:Two-Hybrid System Techniques
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D005656:Fungal Proteins; D000090266:Chromobox Protein Homolog 5; D015254:DNA Modification Methylases; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase