Substitutions in the Amino-Terminal Tail of Neurospora Histone H3 Have Varied Effects on DNA Methylation
Substitutions in the Amino-Terminal Tail of Neurospora Histone H3 Have Varied Effects on DNA Methylation
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DOI：
10.1371/journal.pgen.1002423
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发表时间：
2011-12-01
期刊：
影响因子：
4.5
通讯作者：
Selker, Eric U.
中科院分区：
文献类型：
--
作者：
Adhvaryu, Keyur K.;Berge, Emanuela;Selker, Eric U.
真核基因组分别分别为活性和非活性结构域，分别称为白染料和异染色质。在Neurospora crassa中，异染色质形成需要Set域蛋白DIM-5在赖氨酸9（H3K9）处组蛋白H3的甲基化。异染色质蛋白1（HP1）读取此标记，并直接募集DNA甲基转移酶Dim-2。在存在野生型HH3（HH3（HH3（wt）））的情况下，携带k9（HH3（K9L）或HH3（K9R））替代的异位H3基因会导致DNA甲基化的全局损失。我们研究了H3的N末端尾部中的其他残基是否对于DNA和H3K9的甲基化重要。在存在或不存在野生型等位基因的情况下，生成了H3的N末端尾部的突变，并在体外和体内进行了测试。在没有野生型等位基因的情况下，K4，K9，T11，G12，G13，K14，K14，K27，S28和K36的取代是致命的。相反，带有R2，A7，R8，S10，A15，P16，R17，K18和K23的突变体可行。取代对DNA甲基化的影响是可变的。有些是隐性的，另一些则导致DNA甲基化的半主流损失。 R2，A7，R8，S10，T11，G12，G13，K14和P16的取代导致体内DNA甲基化的部分或完全丧失。在体外DIM-5活性仅需要残基R8-G12。 DIM-5活性通过H3K4的二甲基化和H3S10的磷酸化抑制，而不是通过H3K14的乙酰化来抑制。我们得出的结论是，H3尾部是影响DNA甲基化的信号的集成平台，部分通过H3K9的甲基化。
Eukaryotic genomes are partitioned into active and inactive domains called euchromatin and heterochromatin, respectively. In Neurospora crassa, heterochromatin formation requires methylation of histone H3 at lysine 9 (H3K9) by the SET domain protein DIM-5. Heterochromatin protein 1 (HP1) reads this mark and directly recruits the DNA methyltransferase, DIM-2. An ectopic H3 gene carrying a substitution at K9 (hH3(K9L) or hH3(K9R)) causes global loss of DNA methylation in the presence of wild-type hH3 (hH3(WT)). We investigated whether other residues in the N-terminal tail of H3 are important for methylation of DNA and of H3K9. Mutations in the N-terminal tail of H3 were generated and tested for effects in vitro and in vivo, in the presence or absence of the wild-type allele. Substitutions at K4, K9, T11, G12, G13, K14, K27, S28, and K36 were lethal in the absence of a wild-type allele. In contrast, mutants bearing substitutions of R2, A7, R8, S10, A15, P16, R17, K18, and K23 were viable. The effect of substitutions on DNA methylation were variable; some were recessive and others caused a semidominant loss of DNA methylation. Substitutions of R2, A7, R8, S10, T11, G12, G13, K14, and P16 caused partial or complete loss of DNA methylation in vivo. Only residues R8-G12 were required for DIM-5 activity in vitro. DIM-5 activity was inhibited by dimethylation of H3K4 and by phosphorylation of H3S10, but not by acetylation of H3K14. We conclude that the H3 tail acts as an integrating platform for signals that influence DNA methylation, in part through methylation of H3K9.