Role of histone H3 phosphorylation in transcription and chromatin structure

组蛋白氨基末端尾部的共价修饰是调节染色质结构和调控转录的重要机制。特别是，组蛋白H3和H4尾部赖氨酸残基的乙酰化和甲基化似乎建立了一个用于招募其他蛋白质和改变染色质结构的密码。组蛋白H3磷酸化在Ser10中的作用研究较少，其改变染色质结构的机制也不清楚。这种修饰似乎是有丝分裂期间染色体凝聚或间期期间转录激活的信号，但这些明显不同作用的基础尚不清楚。同样未知的是，这种修饰在多大程度上用于调节基因表达，受H3磷酸化影响的转录方面，以及控制ser10磷酸化H3水平所涉及的酶或调节活性。提出的实验解决了H3磷酸化是如何调节的问题，以及它在果蝇转录和染色质结构控制中的作用。H3 Ser10磷酸化水平似乎是转录活性的决定因素。磷酸化H3的数量应取决于作用于该组蛋白的蛋白激酶和蛋白磷酸酶的活性。初步结果表明JIL-1激酶和PP2A磷酸酶是参与这一过程的两个关键酶。实验将试图证实这两种酶的参与和/或确定参与H3磷酸化的其他磷酸酶。SET和pp32蛋白已被证明在体外调节PP2A活性，并抑制H3乙酰化。因此，这两种蛋白可能是控制组蛋白H3磷酸化和乙酰化之间相互作用的开关的一部分。将采用遗传和分子结合的方法来表征这两种蛋白，并研究它们在体内控制共价组蛋白修饰的功能。最后，将对JIL-1突变表型的修饰因子进行遗传筛选，以确定参与控制H3磷酸化和染色质凝聚的其他因素。该研究项目将作为教学计划的教育基础，旨在教育巴尔的摩公立高中学生从事生物医学科学职业。一系列的教育活动将有两个目标：增加约翰霍普金斯大学来自贫困背景的本科生的数量，并通过在实验室的体验式学习，在高中和霍普金斯大学对这些学生进行尖端生物学研究的培训和指导。

Covalent modification of histone amino-terminal tails is an important mechanism used to modulate chromatin structure and regulate transcription. In particular, acetylation and methylation of Lys residues in the tails of histones H3 and H4 appear to establish a code that serves to recruit other proteins and alter chromatin structure. The role of histone H3 phosphorylation in Ser10 has been less studied and the mechanisms by which it alters chromatin structure are not understood. This modification appears to be a signal for either chromosome condensation during mitosis or transcription activation during interphase, but the basis for these apparently divergent roles is not known. Also unknown are the extent to which this modification is used to regulate gene expression, the aspects of transcription affected by H3 phosphorylation and the enzymatic or regulatory activities involved in controlling the levels of Ser10-phosphorylated H3. Proposed experiments address the question of how H3 phosphorylation is regulated and what its role is in the control of transcription and chromatin structure in Drosophila. The level of H3 Ser10 phosphorylation appears to be a determinant of transcription activity. The amount of phosphorylated H3 should depend on the activities of protein kinases and protein phosphatases acting on this histone. Preliminary results point to the JIL-1 kinase and PP2A phosphatase as two critical enzymes involved in this process. Experiments will attempt to confirm the involvement of these two enzymes and/or identify additional phosphatases involved in H3 phosphorylation. The proteins SET and pp32 have been shown to regulate PP2A activity in vitro, as well as to inhibit H3 acetylation. Therefore, these two proteins may be part of a switch that controls the interplay between histone H3 phosphorylation and acetylation. A combination of genetic and molecular approaches will be used to characterize these two proteins and study their in vivo function in the control of covalent histone modification. Finally, a genetic screen for modifiers of the JIL-1 mutant phenotype will be carried out in order to identify other factors involved in the control of H3 phosphorylation and chromatin condensation.This research project will serve as the educational basis for an instructional program aimed at educating Baltimore public high school students in biomedical science careers. A series of educational activities will be carried out with two objectives: increasing the number of undergraduate students from underprivileged backgrounds at Johns Hopkins and training and mentoring these students while in high school and at Hopkins in cutting edge biological research through experiential learning in the laboratory.