The role of tmRNA in development of C. crescentus

描述（由申请人提供）：通过非编码rna （ncRNAs）调控基因表达是生物学中的一个新兴范例。在从噬菌体到人类的各种生物中，ncRNAs调节多种过程，包括转录、翻译、RNA修饰、mRNA稳定性、RNA剪接、染色质结构、蛋白质稳定性和活性。真核生物和原核生物基因组包含数百个未表征的ncrna，这些基因已越来越多地被确定为导致发育缺陷和几种人类疾病的突变位点。这些ncrna中最有趣的是tmRNA，一种具有tRNA和mRNA特性的分子，它可以干预选定的翻译反应，tmRNA识别选定的翻译复合物并进入核糖体介导在新生多肽上添加肽标签，靶向蛋白质快速降解并释放核糖体和mRNA。这种独特的活性在翻译质量控制机制和基因表达调控中都起作用。tmRNA在整个细菌王国中是保守的，并且在诸如发病机制、共生、胁迫耐受性和细菌发育等过程中是必需的。本课题的长期目标是了解tmRNA在细菌中的作用机制和生理作用。本文将重点研究tmRNA在新月茎杆菌的发育和细胞周期调控中的作用。月牙草是这些研究的首选生物，因为对控制其细胞周期和发育程序的分子事件的广泛了解为确定tmRNA活性对细胞分化和DNA复制的影响提供了独特的机会。tmRNA是月牙草DNA复制的适当时机和从群细胞向柄细胞同步分化所必需的。本研究的主要目标是：鉴定月牙草中对DNA复制控制重要的tmRNA底物，确定这些底物上的tmRNA活性如何影响DNA复制，并了解细胞遗传调控网络如何控制tmRNA活性。

DESCRIPTION (provided by applicant): Regulation of gene expression by noncoding RNAs (ncRNAs) is an emerging paradigm in biology. ncRNAs regulate a variety of processes, including transcription, translation, RNA modification, mRNA stability, RNA splicing, chromatin structure, and protein stability and activity, in a wide variety of organisms from bacteriophages to humans. Eukaryotic and prokaryotic genomes contain hundreds of uncharacterized ncRNAs, and these genes have been increasingly identified as the loci of mutations that cause developmental defects and several human diseases. One of the most interesting of these ncRNAs is tmRNA, a molecule with properties of both a tRNA and an mRNA, which intervenes in selected translation reactions, tmRNA recognizes selected translation complexes and enters the ribosome to mediate the addition of a peptide tag to the nascent polypeptide, targeting the protein for rapid degradation and releasing the ribosome and mRNA. This unique activity functions both in a translational quality control mechanism and in regulation of gene expression. tmRNA is conserved throughout the bacterial kingdom, and is required for processes such as pathogenesis, symbiosis, stress tolerance, and bacterial development. The long-term objective of this proposal is to understand the mechanism of action and physiological role of tmRNA in bacteria. This proposal focuses on the role of tmRNA in the development and cell cycle regulation of Caulobacter crescentus. C. crescentus is the organism of choice for these studies because the extensive knowledge of the molecular events that control its cell cycle and developmental program provide a unique opportunity to determine the influence of tmRNA activity on cellular differentiation and DNA replication. tmRNA is required for proper timing of DNA replication and the coincident differentiation from swarmer cell to stalked cell in C. crescentus. The primary goals of this proposal are: to identify substrates for tmRNA in C. crescentus that are important for control of DNA replication, to determine how tmRNA activity on these substrates affects DNA replication, and to understand how the activity of tmRNA is controlled by the genetic regulatory network of the cell.