题　目：Roles of H3K4me3 in Transcriptional regulation and dehydration memory
报告人：Yong Ding，Professor, University of Science and Technology of China
主持人：许 玲 教授
时　间：10月23日 13:30-14:30（周三）
地　点：闵行校区生命科学学院534报告厅

报告人简介：丁勇，中国科学技术大学生命科学院教授、博士生导师。 1997年毕业于安徽农业大学获农学学士学位; 2007年获中国科学院遗传与发育生物学研究所理学博士; 2007-2010年分别在德州大学西南医学中心和内布拉斯加大学林肯分校从事博士后研究工作; 2011-2012年8月在内布拉斯加大学林肯分校任研究助理教授，2012年9月任中国科学技术大学生命科学院教授。

报告内容简介：The Arabidopsis thaliana trithorax-like protein, ATX1, shares common structural domains, has similar histone methyltransferase (HMT) activity, and belongs in the same phylogenetic subgroup as its animal counterparts. Most of our knowledge of the role of HMTs in trimethylating lysine 4 of histone H3 (H3K4me3) in transcriptional regulation comes from studies of yeast and mammalian homologs. Little is known about the mechanism by which ATX1, or any other HMT of plant origin, affects transcription. Here, we provide insights into how ATX1 influences transcription at regulated genes, playing two distinct roles. At promoters, ATX1 is required for TATA binding protein (TBP) and RNA Polymerase II (Pol II) recruitment. In a subsequent event, ATX1 is recruited by a phosphorylated form of Pol II to the +300-bp region of transcribed sequences, where it trimethylates nucleosomes. Point mutations in the catalytic domain of ATX1 (ARABIDOPSIS TRITHORAX1), a H3K4 methyltransferase, and RNAi knockdowns of subunits of the AtCOMPASS–like (Arabidopsis Complex Proteins Associated with Set) were used to address this question. We demonstrate that both ATX1 and AtCOMPASS–like are required for high level accumulation of TBP (TATA-binding protein) and Pol II at promoters and that this requirement is independent of the catalytic histone modifying activity. However, the catalytic function is critically required for transcription as H3K4me3 levels determine the efficiency of transcription elongation. The roles of H3K4me3, ATX1, and AtCOMPASS–like may be of a general relevance for transcription of Trithorax-activated eukaryotic genes. Moreover, Multiple stress alter plants’ subsequent responses by producing faster and/or stronger reactions implying that plants exercise a form of ‘stress memory’. we show that during recurring dehydration stresses Arabidopsis plants display transcriptional stress memory demonstrated by an increase in the rate of transcription and elevated transcript levels of a subset of the stress–response genes (trainable genes). During recovery (watered) states, trainable genes produce transcripts at basal (preinduced) levels, but remain associated with atypically high H3K4me3 and Ser5P polymerase II levels, indicating that RNA polymerase II is stalled. This is the first example of a stalled RNA polymerase II and its involvement in transcriptional memory in plants.