Factors Controlling the Entry Into Productive Elongation by RNA Polymerase II PDF Download
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Author: Nicholas F. Marshall
Publisher:
ISBN:
Category : Drosophila
Languages : en
Pages : 320
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Author: Nicholas F. Marshall
Publisher:
ISBN:
Category : Drosophila
Languages : en
Pages : 320
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Author: Zhiyuan Yang
Publisher:
ISBN:
Category :
Languages : en
Pages : 302
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Author: Nicholas James Fuda
Publisher:
ISBN:
Category :
Languages : en
Pages : 202
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Most gene expression is regulated at the level of transcription, and the transition from initiation to productive elongation is a key point of regulation. This transition is accompanied by pausing of transcriptionally engaged polymerase in the promoter-proximal region of several heat shock genes. Although this mechanism of regulation was long thought to be limited to a few genes, recent evidence has indicated that pausing is wide-spread in higher eukaryotes. Therefore, it is increasingly important to understand the mechanisms controlling the paused polymerase. I have investigated how the site of pausing on Hsp70 is specified using highresolution mapping of polymerase on reporter genes with shifted pausing site sequences. The results indicate that the downstream sequence dictates pause position and the overall level of pausing. I have also used RNAi knock-down in Drosophila cell culture to study the roles of several factors in establishing, maintaining, and releasing the paused polymerase. These experiments have shown GAGA factor is required for pausing on many of its target genes, and the knock-down effects indicate it is involved in establishing the pause. In contrast, Spt5, a protein previously shown to enhance pausing in vitro, reduces pausing genome-wide by increasing levels of elongating polymerase. Two kinases, P-TEFb and CDK12, function in productive elongation. Previously our lab showed that P-TEFb inhibition prevented the transition into elongation, limiting the polymerase to the 5' end of the heat shock-induced Hsp70 gene. I mapped these polymerases in high resolution to show they occupied sites further downstream than the normal pause sites, suggesting P-TEFb activity may not solely release the paused polymerase. I also determined the localization of CDK12 on active genes. Its localization downstream of P-TEFb suggests that these kinases may have distinct functions. Finally, I have examined the role of Fcp1 in Hsp70 transcription. Our lab previously showed the CTD phosphatase Fcp1 was required for optimum expression of Hsp70 mRNA. Fcp1 knock-down reduced the heat shock levels of Pol II and increased phosphorylation of nonchromatin bound Pol II, indicating that Fcp1 recycling of RNA polymerase II to an initiationcompetent form is required for optimal Hsp70 heat shock transcription.
Author: Ronald C. Conaway
Publisher: Raven Press (ID)
ISBN:
Category : Science
Languages : en
Pages : 600
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Presents a coherent account of many productive lines of investigation, organized as a series of mini-reviews that focus on major research areas including studies on the structure and mechanisms of action of bacterial, viral, and eukaryotic RNA polymerases, and the transcription factors that control their activities. Each review provides a brief but up-to-date account of the progress of research in a particular area, a discussion of the major issues and questions driving that research, and a brief description of the evolving approaches and technologies used to address those questions. Annotation copyright by Book News, Inc., Portland, OR
Author: Torben Heick Jensen
Publisher: Springer Science & Business Media
ISBN: 1441978410
Category : Medical
Languages : en
Pages : 161
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Book Description
The diversity of RNAs inside living cells is amazing. We have known of the more “classic” RNA species: mRNA, tRNA, rRNA, snRNA and snoRNA for some time now, but in a steady stream new types of molecules are being described as it is becoming clear that most of the genomic information of cells ends up in RNA. To deal with the enormous load of resulting RNA processing and degradation reactions, cells need adequate and efficient molecular machines. The RNA exosome is arising as a major facilitator to this effect. Structural and functional data gathered over the last decade have illustrated the biochemical importance of this multimeric complex and its many co-factors, revealing its enormous regulatory power. By gathering some of the most prominent researchers in the exosome field, it is the aim of this volume to introduce this fascinating protein complex as well as to give a timely and rich account of its many functions. The exosome was discovered more than a decade ago by Phil Mitchell and David Tollervey by its ability to trim the 3’end of yeast, S. cerevisiae, 5. 8S rRNA. In a historic account they laid out the events surrounding this identification and the subsequent birth of the research field. In the chapter by Kurt Januszyk and Christopher Lima the structural organization of eukaryotic exosomes and their evolutionary counterparts in bacteria and archaea are discussed in large part through presentation of structures.
Author: Manchuta Dangkulwanich
Publisher:
ISBN:
Category :
Languages : en
Pages : 137
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The expression of a gene begins by transcribing a target region on the DNA to form a molecule of messenger RNA. As transcription is the first step of gene expression, it is there- fore highly regulated. The regulation of transcription is essential in fundamental biological processes, such as cell growth, development and differentiation. The process is carried out by an enzyme, RNA polymerase, which catalyzes the addition of a nucleotide complementary to the template and moves along the DNA one base pair at a time. To complete its tasks, the enzyme functions as a complex molecular machine, possessing various evolutionarily designed parts. In eukaryotes, RNA polymerase has to transcribe through DNA wrapped around histone proteins forming nucleosomes. These structures represent physical barriers to the transcribing enzyme. In chapter 2, we investigated how each nucleosomal component--the histone tails, the specific histone-DNA contacts, and the DNA sequence--contributes to the strength of the barrier. Removal of the tails favors progression of RNA polymerase II into the entry region of the nucleosome by locally increasing the wrapping-unwrapping rates of the DNA around histones. In contrast, point mutations that affect histone-DNA contacts at the dyad abolish the barrier to transcription in the central region by decreasing the local wrapping rate. Moreover, we showed that the nucleosome amplifies sequence-dependent transcriptional pausing, an effect mediated through the structure of the nascent RNA. Each of these nucleosomal elements controls transcription elongation by distinctly affecting the density and duration of polymerase pauses, thus providing multiple and alternative mechanisms for control of gene expression by additional factors. During transcription elongation, RNA polymerase has been assumed to attain equilibrium between pre- and post-translocated states rapidly relative to the subsequent catalysis. Under this assumption, a branched Brownian ratchet mechanism that necessitates a putative secondary nucleotide binding site on the enzyme was proposed. In chapter 3, we challenged individual yeast RNA polymerase II (Pol II) with a nucleosome as a "road block", and separately measured the forward and reverse translocation rates with our single-molecule transcription elongation assay. Surprisingly, we found that the forward translocation rate is comparable to the catalysis rate. This finding reveals a linear, non-branched ratchet mech-anism for the nucleotide addition cycle in which translocation is one of the rate-limiting steps. We further determined all the major on- and off-pathway kinetic parameters in the elongation cycle. This kinetic model provides a framework to study the influence of various factors on transcription dynamics. To further dissect the operation of Pol II, we focused on the trigger loop, a mobile element near the active site of the enzyme. Biochemical and structural studies have demonstrated that the trigger loop makes direct contacts with substrates and promotes nucleotide incorporation. It is also an important regulatory element for transcription fidelity. In chapter 4, we characterized the dynamics of a trigger loop mutant RNA polymerase to elucidate the roles of this element in transcription regulation, and applied the above kinetic framework to quantify the effects of the mutation. In comparison to the wild-type enzyme, we found that the mutant is more sensitive to force, faster at substrate sequestration, and more efficient to return from a pause to active transcription. This work highlighted important roles of regulatory elements in controlling transcription dynamics and fidelity. Moreover, RNA polymerase interacts with various additional factors, which add layers of regulation on transcription. Transcription factors IIS (TFIIS) and IIF (TFIIF) are known to interact with elongating RNA polymerase directly and stimulate transcription. In chapter 5, we studied the effects of these factors on elongation dynamics using our single molecule assay. We found that both TFIIS and TFIIF enhance the overall transcription elongation by reducing the lifetime of transcriptional pauses and that TFIIF also decreases the probability of pause entry. Furthermore, we observed that both factors enhance the efficiency of nucleosomal transcription. Our findings helped elucidate the molecular mechanisms of gene expression modulation by transcription factors. In summary, we have dissected the mechanisms by which the nucleosomal elements regulate transcription, and derived a quantitative kinetic model of transcription elongation in a linear Brownian ratchet scheme with the slow translocation of the enzyme. The corresponding translocation energy landscape shows that the off-pathway states are favored thermodynamically but not kinetically over the on-pathway states. This observation confers the enzyme its high propensity to pause, thus allowing additional regulatory mechanisms during pausing. TFIIS and TFIIF, for example, regulate transcription dynamics by shortening the lifetime of Pol II pauses. On the other hand, the trigger loop of Pol II regulates both the active elongation and pausing. These examples illustrate molecular mechanisms of cis- and trans-acting factors regulate the dynamics of transcription elongation.
Author: Chun-hsiang Chang
Publisher:
ISBN:
Category : RNA polymerases
Languages : en
Pages : 336
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Author: Renato Paro
Publisher: Springer Nature
ISBN: 3030686701
Category : Science
Languages : en
Pages : 215
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This open access textbook leads the reader from basic concepts of chromatin structure and function and RNA mechanisms to the understanding of epigenetics, imprinting, regeneration and reprogramming. The textbook treats epigenetic phenomena in animals, as well as plants. Written by four internationally known experts and senior lecturers in this field, it provides a valuable tool for Master- and PhD- students who need to comprehend the principles of epigenetics, or wish to gain a deeper knowledge in this field. After reading this book, the student will: Have an understanding of the basic toolbox of epigenetic regulation Know how genetic and epigenetic information layers are interconnected Be able to explain complex epigenetic phenomena by understanding the structures and principles of the underlying molecular mechanisms Understand how misregulated epigenetic mechanisms can lead to disease
Author: Guido Silvestri
Publisher: Springer
ISBN: 303002816X
Category : Medical
Languages : en
Pages : 253
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Book Description
This volume summarizes recent advances in understanding the mechanisms of HIV-1 latency, in characterizing residual viral reservoirs, and in developing targeted interventions to reduce HIV-1 persistence during antiretroviral therapy. Specific chapters address the molecular mechanisms that govern and regulate HIV-1 transcription and latency; assays and technical approaches to quantify viral reservoirs in humans and animal models; the complex interchange between viral reservoirs and the host immune system; computational strategies to model viral reservoir dynamics; and the development of therapeutic approaches that target viral reservoir cells. With contributions from an interdisciplinary group of investigators that cover a broad spectrum of subjects, from molecular virology to proof-of-principle clinical trials, this book is a valuable resource for basic scientists, translational investigators, infectious-disease physicians, individuals living with HIV/AIDS and the general public.
Author:
Publisher:
ISBN: 9780815332183
Category : Cells
Languages : en
Pages : 0
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