definingpirnaprimarytranscripts：定义类的初级转录物

Cell Cycle 1657Cell Cycle 12:11, 1657–1658; June 1, 2013; © 2013 Landes Bioscience
EditoriaLs: CELL CyCLE FEaturEs EditoriaLs: CELL CyCLE FEaturEs PIWI proteins and their associated small
RNAs (PIWI-interacting RNAs, piR-
NAs) are essential for fertility in mam-
mals.1,2 piRNAs (24–35 nt) are longer
than miRNAs (21–23 nt) and have
2'-O -methyl-modified 3' termini.3-6
Like miRNAs, piRNAs bind members
of the Argonaute family of proteins, but
piRNAs are unique in that they guide
PIWI proteins, a specialized subfamily
of Argonaute proteins that are expressed
mainly in germ cells.1 The sequences of
piRNAs are more diverse than any other
known class of cellular RNAs. For exam-
ple, our 8.8 million piRNA reads in a
deep sequencing library from adult mouse
testis comprised 2.7 million different
piRNAs; > 90% of piRNA species were
sequenced just once.
piRNAs map to large blocks of
genomic sequence called clusters.4,5 The
architecture of piRNA clusters suggests
that mature piRNAs derive from precur-
sor transcripts via multiple RNA process-
ing steps. While > 80% of piRNA reads
in flies map to transposons, ~93% of
adult mouse piRNA reads map to a single
site in the genome. That so many mouse
piRNAs map uniquely to the genome
facilitates the study of their precursor
transcripts. Using total RNA sequencing,
we detected long RNAs (> 100 nt) from
piRNA clusters. Chromatin immunopre-
cipitation of RNA polymerase II and III
suggests that these transcripts are tran-
scribed by RNA polymerase II. Consistent
with mouse piRNA precursors being RNA
polymerase II transcripts, the long RNAs
bear a standard cap structure (detected by
cap analysis of gene expression; CAGE), and their 3' ends possess a poly(A) tail Defining piRNA primary transcripts
Xin Zhiguo Li, Christian K. roy, Melissa J. Moore and Phillip d. Zamore*
Howard Hughes Medical institute; rNa therapeutics institute and department of Biochemistry and Molecular Pharmacology; university of Massachusetts Medical school; Worcester, Ma usa
*Correspondenceto:PlillipD.Zamore;Email:***************************
Submitted: 04/22/13; Accepted: 04/23/13
/10.4161/cc.24989
Comment on: Li XZ, et al. Mol Cell 2013; 50:67-81; PMID:23523368; /10.1016/j.molcel.2013.02.016
(detected by polyadenylation site sequenc-ing; PAS-seq).7Historically, piRNA clusters have been defined computationally using mature piRNA sequences. Thus, clus-ters are not transcriptional units. When we began our studies, it was unknown whether piRNAs originated from sin-gle continuous transcripts or multiple short transcripts, as they do in nema-todes. The location of piRNA precursor transcription start sites (TSSs) and pro-moters or whether they are spliced was also unknown. We discovered the first transcription factor regulating piRNA biogenesis by analyzing a subset of 15 clusters that appeared to be transcribed bidirectionally. In these clusters, a short piRNA region lacking piRNA separates piRNAs mapping to the genomic minus strand from those mapping to the plus strand. These putative bidirectional pro-moter regions contain binding motifs for the MYB family of transcription fac-tors (E = 8.3 × 10−12). We used the sub-set of clusters for motif finding, because the computationally defined bound-ary of most clusters is more than 3 kbp away from experimentally determined TSSs. Accurately annotating the TSSs of piRNA cluster transcripts allowed us to discover that MYB motifs are signifi-cantly enriched (E = 9.1 × 10−28) in 100 piRNA promoters, including both bidi-rectional and unidirectional transcribed clusters.7 This allowed us to define the transcription units of piRNA-producing loci and replace the previous computa-tionally defined cluster annotations.We identified primary piRNA tran-scripts by a combination of de novo and reference-based transcript assembly using paired-end total RNA sequencing. We further corrected the ends of these tran-scripts using CAGE and PAS. Our data allowed us to define 467 piRNA precursor transcripts derived from 214 piRNA-pro-ducing loci.7 The 214 loci constitute just 0.33% of the mouse genome yet account for 95% of piRNAs in the adult mouse testis.The 214 loci can be divided into two different types of piRNA-producing genes. Genic piRNA loci are known pro-tein-coding genes that also produce piR-NAs and are mostly expressed during early spermatogenesis before the pachytene stage of meiosis. Historically, piRNAs mapping to these genes have been referred to as pre-pachytene piRNAs.8 Intergenic piRNA loci lie far in the genome from other annotated genes. Most piRNAs from these loci are detected after 12.5 days postpartum and have been called pachy-tene piRNA clusters.The transcription factor A-MYB binds at the promoters of the pachytene piRNA-producing loci, and the loss of A-Myb depleted both piRNA precursor tran-scripts as well as mature piRNAs across the length of the loci.7 Thus, our data represent the first formal demonstration that long RNA polymerase II transcripts are the precursors of mature piRNAs in mammals. That is, piRNAs are derived from long, continuous RNAs that are subsequently fragmented and processed into piRNAs (Fig. 1). The set of piRNA loci and well-annotated piRNA precursor transcripts defined by our work provide an invaluable resource for further study of piRNA biogenesis and function.
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org/10.1242/dev.00973
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ence.1130164
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ence.1142612
Figure 1. a model for pirNa biogenesis. Primary pirNa transcripts are transcribed by rNa poly-
merase ii and contain 5' caps, exons and introns and poly(a) tails. the transcription of pachytene
pirNa genes is controlled by a-MyB; transcription factor(s) (tF) controlling pre-pachytene pirNa
genes remain to be discovered. Current models of pirNa biogenesis propose that PLd6 deter-
mines the 5' end of pirNa intermediates with lengths > 30 nt. these intermediates are proposed
to then be loaded into PiWi proteins. after PiWi binding, a nuclease is thought to trim the 3' end
of the pirNa to the length characteristic of the particular bound PiWi protein. Finally, further trim-
ming is prevented by addition of a 2'-O-methyl group to the 3' end of the mature pirNa by the
-adenosylmethionine-dependent methyltransferase Hen1.
1658 Cell Cycle Volume 12 issue 11
Below is given annual work summary, do not need friends can download after editor deleted Welcome to visit again
XXXX annual work summary
Dear every leader, colleagues:
Look back end of XXXX, XXXX years of work, have the joy of success in your work, have a collaboration with colleagues, working hard, also have disappointed when encountered difficulties and setbacks. Imperceptible in tense and orderly to be over a year, a year, under the loving care and guidance of the leadership of the company, under the support and help of colleagues, through their own efforts, various aspects have made certain progress, better to complete the job. For better work, sum up experience and lessons, will now work a brief summary.
To continuously strengthen learning, improve their comprehensive quality. With good comprehensive quality is the precondition of completes the labor of duty and conditions. A year always put learning in the important position, trying to improve their comprehensive quality. Continuous learning professional skills, learn from surrounding colleagues with rich work experience, equip themselves with knowledge, the expanded aspect of knowledge, efforts to improve their comprehensive quality.
The second Do best, strictly perform their responsibilities. Set up the company, to maximize the customer to the satisfaction of the company's products, do a good job in technical services and product promotion to the company. And collected on the properties of the products of the company, in order to make improvement in time, make the products better meet the using demand of the scene.
Three to learn to be good at communication, coordinating assistance. On‐site technical service personnel should not only have strong professional technology, should also have good communication ability, a lot of a product due to improper operation to appear problem, but often not customers reflect the quality of no, so this time we need to find out the crux, and customer communication, standardized operation, to avoid customer's mistrust of the products and even the damage of the company's image. Some experiences in the past work, mentality is very important in the work, work to have passion, keep the smile of sunshine, can close the distance between people, easy to communicate with the customer. Do better in the daily work to communicate with customers and achieve customer satisfaction, excellent technical service every time, on behalf of the customer on our products much a understanding and trust.
Fourth, we need to continue to learn professional knowledge, do practical grasp skilled operation. Over the past year, through continuous learning and fumble, studied the gas generation, collection and methods, gradually familiar with and master the company introduced the working principle, operation method of gas machine. With the help of the department leaders and colleagues, familiar with and master the launch of the division principle, debugging method of the control system, and to wuhan Chen Guchong garbage power plant of gas machine control system transformation, learn to debug, accumulated some experience. All in all, over the past year, did some work, have also made some achievements, but the results can only represent the past, there are some problems to work, can't meet the higher requirements. In the future work, I must develop the oneself advantage, lack of correct, foster strengths and circumvent weaknesses, for greater achievements. Looking forward to XXXX years of work, I'll be more efforts, constant progress in their jobs, make greater achievements. Every year I have progress, the growth of believe will get greater returns, I will my biggest contribution to the development of the company, believe in
yourself do better next year!
I wish you all work study progress in the year to come.。