DNA methylation and the formation of heterochromatin in Neurospora crassa.

Studies of the control and function of DNA methylation in Neurospora crassa have led to a greater understanding of heterochromatin formation. DNA methylation in Neurospora is dependent on trimethylation of histone H3 lysine 9 (H3K9me3) by the histone methyltransferase, DIM-5. The linkage between these two methyl marks is facilitated by heterochromatin protein 1 (HP1), which serves as an adapter protein. HP1 binds to the H3K9me3 and recruits the DNA methyltransferase, DIM-2. Although HP1 links H3K9me3 to DNA methylation, it also serves to recruit the DNA methylation modifier complex to the edges of heterochromatin regions, where it serves to limit the spreading of the heterochromatin by countering H3K9me3.