Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, MB R3E0V9, Canada.
Biochem Cell Biol. 2009 Oct;87(5):695-709. doi: 10.1139/O09-053.
Chromatin condensation and subsequent decondensation are processes required for proper execution of various cellular events. During mitosis, chromatin compaction is at its highest, whereas relaxation of chromatin is necessary for DNA replication, repair, recombination, and gene transcription. Since histone proteins are directly complexed with DNA in the form of a nucleosome, great emphasis is put on deciphering histone post-translational modifications that control the chromatin condensation state. Histone H3 phosphorylation is a mark present in mitosis, where chromatin condensation is necessary, and in transcriptional activation of genes, when chromatin needs to be decondensed. There are four characterized phospho residues within the H3 N-terminal tail during mitosis: Thr3, Ser10, Thr11, and Ser28. Interestingly, H3 phosphorylated at Ser10, Thr11, and Ser28 has been observed on genomic regions of transcriptionally active genes. Therefore, H3 phosphorylation is involved in processes requiring opposing chromatin states. The level of H3 phosphorylation is mediated by opposing actions of specific kinases and phosphatases during mitosis and gene transcription. The cellular contexts under which specific residues on H3 are phosphorylated in mitosis and interphase are known to some extent. However, the functional consequences of H3 phosphorylation are still unclear.
染色质凝聚和随后的解凝聚是执行各种细胞事件所必需的过程。在有丝分裂过程中，染色质的紧缩达到最高水平，而染色质的松弛对于 DNA 复制、修复、重组和基因转录是必要的。由于组蛋白蛋白以核小体的形式直接与 DNA 复合，因此非常重视破译控制染色质凝聚状态的组蛋白翻译后修饰。组蛋白 H3 磷酸化是有丝分裂中存在的一个标记，在有丝分裂中需要染色质凝聚，在基因转录激活时需要解凝聚染色质。在有丝分裂期间，H3 N 端尾部有四个特征磷酸化残基：Thr3、Ser10、Thr11 和 Ser28。有趣的是，在转录活跃基因的基因组区域观察到 Ser10、Thr11 和 Ser28 磷酸化的 H3。因此，H3 磷酸化参与需要相反染色质状态的过程。在有丝分裂和基因转录过程中，特定激酶和磷酸酶的拮抗作用介导 H3 磷酸化水平。在有丝分裂和间期中 H3 上特定残基被磷酸化的细胞环境在某种程度上是已知的。然而，H3 磷酸化的功能后果仍不清楚。
