Liu Hongde, Luo Kun, Zhou Zikai, Mu Yawen, Wan Yakun
*State Key Laboratory of Bioelectronics, Southeast University, Nanjing 210096, China.
†Department of Neurosurgery, Xinjiang Evidence-Based Medicine Research Institute, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830054, China.
Biochem J. 2014 Jun 15;460(3):387-97. doi: 10.1042/BJ20140186.
Htz1 (histone 2A Z1) deposition at promoters is involved in the transcriptional activation of quiescent genes. Chz1 [chaperone for Htz1 (or H2A)-H2B dimer] is an Htz1-H2B-specific chaperone that delivers histone H2A.Z that substitutes for H2A. Spt16 (suppressor of Ty) functions in transcription elongation and also possesses a histone chaperone activity. However, the links among Chz1, Htz1 and Spt16 remain unknown. In the present study, we determined the genomic binding profiling of Htz1, Pol II (RNA polymerase II) and Spt16 using ChIP microarray experiments and sequenced nucleosomal DNA using a next-generation sequencing technique in wild-type and chz1-deletion strains of Saccharomyces cerevisiae. The results of the present study revealed that Spt16 and Pol II are associated, bind at nucleosome-depleted regions, and are positively correlated with the transcription rate. Importantly, Spt16 disfavours the Htz1-bound genes, and this discrimination is impaired upon the deletion of chz1. The negative correlation between the binding profiles of Spt16 and Htz1 at promoters is not an intrinsic repulsion, but is probably due to a requirement for transcription initiation. We showed that chz1 deletion decreases Htz1 binding at promoters and telomeres. Also, in the chz1-deletion mutant, Spt16 binding at ribosomal genes was lost. The results of the present study suggest that the discrimination of Spt16 to Htz1-bound genes is due to the priority of Chz1 over Spt16 in binding to the Htz1-bound genomic regions. Chz1-escorted Htz1 therefore impairs Spt16 binding at chromatin.
启动子处的Htz1（组蛋白2A Z1）沉积参与静止基因的转录激活。Chz1 [Htz1（或H2A）-H2B二聚体的伴侣蛋白]是一种Htz1-H2B特异性伴侣蛋白，可传递替代H2A的组蛋白H2A.Z。Spt16（Ty抑制因子）在转录延伸中起作用，并且也具有组蛋白伴侣活性。然而，Chz1、Htz1和Spt16之间的联系仍然未知。在本研究中，我们使用染色质免疫沉淀微阵列实验确定了Htz1、Pol II（RNA聚合酶II）和Spt16的基因组结合图谱，并使用下一代测序技术对酿酒酵母野生型和chz1缺失菌株中的核小体DNA进行了测序。本研究结果表明，Spt16与Pol II相关联，结合在核小体缺失区域，并且与转录速率呈正相关。重要的是，Spt16不倾向于结合Htz1的基因，而这种区分在chz1缺失时会受损。启动子处Spt16和Htz1结合图谱之间的负相关不是内在的排斥作用，而可能是由于转录起始的需要。我们表明，chz1缺失会降低启动子和端粒处的Htz1结合。此外，在chz1缺失突变体中，核糖体基因处的Spt16结合丧失。本研究结果表明，Spt16对结合Htz1的基因的区分是由于Chz1在结合Htz1结合的基因组区域方面比Spt16具有优先权。因此，Chz1护送的Htz1会损害Spt16在染色质上的结合。
