Institute of Developmental Biology of Russian Academy of Sciences, Moscow, 119334 Russia.
Biochemistry. 2012 May 29;51(21):4354-63. doi: 10.1021/bi201645c. Epub 2012 May 17.
Functioning of histone lysine methyltransferases (HKMTs) involves interactions of their catalytic domain "SET" with the N-termini of histone H3. However, these interactions are restricted in canonical nucleosomes due to the limited accessibility of H3 termini. Here we investigated whether nucleosome remodeling with the yeast Isw2 affects nucleosome affinity to the SET domain of ALL-1 HKMT. Reconstitution of mononucleosomes by salt dilutions also produces some nucleosome-dimer particles (self-associated mononucleosomes, described by: Tatchell and van Holde (1977) Biochemistry, 16, 5295-5303). The GST-tagged SET-domain polypeptide of ALL-1 was assayed for binding to assembled mononucleosomes and nucleosome-dimer particles, either intact or remodeled with purified yeast Isw2. Remodeling of mononucleosomes does not noticeably affect their affinity to SET domain; however, yIsw2 remodeling of nucleosome-dimer particles facilitated their association with GST-SET polypeptide. Therefore, it is conceivable that nucleosome interactions in trans could be implicated in the maintenance of chromatin methylation patterns in vivo.
组蛋白赖氨酸甲基转移酶（HKMTs）的功能涉及其催化结构域“SET”与组蛋白 H3 N 端的相互作用。然而，由于 H3 末端的有限可及性，这些相互作用在经典核小体中受到限制。在这里，我们研究了酵母 Isw2 的核小体重塑是否会影响 ALL-1 HKMT 的 SET 结构域与核小体的亲和力。通过盐稀释再组装单核小体也会产生一些核小体二聚体颗粒（自我关联的单核小体，由 Tatchell 和 van Holde（1977）描述：生物化学，16，5295-5303）。用 GST 标记的 ALL-1 的 SET 结构域多肽被检测到与组装的单核小体和核小体二聚体颗粒结合，无论是完整的还是用纯化的酵母 Isw2 重塑的。单核小体的重塑不会明显影响其与 SET 结构域的亲和力；然而，核小体二聚体颗粒的 yIsw2 重塑促进了它们与 GST-SET 多肽的结合。因此，可以想象，在体内，核小体之间的相互作用可能与染色质甲基化模式的维持有关。
