一周小结

1. 一周小结 时间：2013年3月13日

2. 依赖型终止子（rut site) • ρ因子的介绍： ρ因子是大肠杆菌的一种基本蛋白质，由6个相同亚基组成，分子量约为275KDa.亚基具有一个RNA结合域和一个ATP水解域。ρ因子是ATP依赖的六聚体解旋酶家族的一员，亚基的RNA结合域在六聚体中央形成一个孔供核算进入，解旋酶从而发挥作用。

3. ρ因子的结构特点 • ρ-依赖型终止作用所需要的序列长50-90个碱基，位于终止子上游。她们的共同特征是RNA富含C而G少。一般来说。一个ρ-依赖型终止子的终止效率随富含C/少G区域的长度的增加而增加

4. 作用机制

5. termination process,Rho at first recognizes 70–80 nt ofunstructured C-richsequence known as rho utilization (rut) site on thenascent RNA through its N-terminal primary RNAbinding site (PBS). This binding event guides the3’-side of the RNA into the central hole of the hexamer,which constitutes the secondary RNA binding site. This inturn activates its ATP hydrolysis and translocase activity,and the latter function is believed to be instrumental indislodging the elongation complex (EC) inside a termin-ation zone, which is usually located 60–90 nts downstreamof the rut site

6. Rho-dependent Termination of Transcription Is Governed Primarilyby the Upstream Rho Utilization (rut) Sequences of a Terminator • 时间：1996年 • 期刊：THE JOURNAL OF BIOLOGICAL CHEMISTRY • 分区：二区 • 影响因子：4.773（2011）

7. A Rho-dependent transcription terminator inEsche-richia coli DNA consists of an upstream part for Rhoutilization (rut) and the transcription stop point (tsp)region. • The upstream part, called rut, encodes a segment of the nascent transcript to which Rho can bind .This interactionbetween Rho and the rut segment of the RNA is essential fortermination • The downstream part, called the transcription stop point (tsp) region, is where termination occurs at several clusters of specific points that are spread over 100 bp of DNA

8. tsp component ofa Rho-dependent terminator are notstringent. • rut is theprimary determinant of a Rho-dependent terminator • the upstream component of the pause site, thepart that encodes the segment of the RNA that can form thestem-loop (hairpin) structure, appears to be a major determinant of the position of the pause, whereas the other sequencesaffect the efficiency and duration of the pause.

9. Rho-dependent terminators and transcriptiontermination • 时间：2006年 • 期刊：Microbiology • 分区：四区 • 影响因子：0.718（2011）

10. 主要内容 • Most Rho-dependent terminators have been found in entericbacteria, but they also occur in Gram-positive bacteria and may be widespread among bacteria.Rho-dependent termination requires both cis-acting elements, on the mRNA, and trans-actingfactors. • ‘auxiliary elements’ may assist in the termination process; they differ among terminators,their occurrence possibly depending on the function and sequence context of the terminator. • NusG, NusA and NusB are additional factors participating in the termination process

13. miRNA: • MicroRNAs（miRNAs）是在真核生物中发现的一类内源性的具有调控功能的非编码RNA，其大小长约20~25个核苷酸。成熟的miRNAs是由较长的初级转录物经过一系列核酸酶的剪切加工而产生的，随后组装进RNA诱导的沉默复合体，通过碱基互补配对的方式识别靶mRNA，并根据互补程度的不同指导沉默复合体降解靶mRNA或者阻遏靶mRNA的翻译。最近的研究表miRNA参与各种各样的调节途径，包括发育、病毒防御、造血过程、器官形成、细胞增殖和凋亡、脂肪代谢等等。

15. Human microRNA prediction through a probabilisticco-learning model of sequence and structure • 时间：2005年 • 期刊：Nucleic Acids Research • 分区：二区 • 影响因子： • 主要内容：基于HMM的算法来识别miRNA

16. HMM

17. Viterbi algorithm • 通过优化得出最可能的状态转移路径并得到其可能的概率

18. Prediction of a mature miRNA region andafunctional strand

19. 预测流程

20. Thank You