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Mozhgan Abasi, Zahra Bazi, Samira Mohammadi-Yeganeh, Masoud Soleimani, Vahid Haghpanah, Nosratollah Zargami, Hossein Ghanbarian
The small nuclear noncoding RNA (snRNA) 7SK is a highly conserved noncoding RNA of 331 nucleotides in animals, which is present in a nuclear ribonucleoprotein complex with proteins such as methylphosphate capping enzyme (MePCE), hexamethylene bisacetamide-inducible proteins 1 and 2 (HEXIM1 and HEXIM2) and La-related protein 7 (Larp7). Regulating the activity of the positive transcription elongation factor b (P-TEFb) is the key function of 7SK noncoding RNA. Recently, we have shown that 7SK snRNA over-expression reduces human embryonic kidney 293T cell line viability...
November 2016: Medical Oncology
Ursula Schulze-Gahmen, Ignacia Echeverria, Goran Stjepanovic, Yun Bai, Huasong Lu, Dina Schneidman-Duhovny, Jennifer A Doudna, Qiang Zhou, Andrej Sali, James H Hurley
HIV-1 Tat hijacks the human superelongation complex (SEC) to promote proviral transcription. Here we report the 5.9 Å structure of HIV-1 TAR in complex with HIV-1 Tat and human AFF4, CDK9, and CycT1. The TAR central loop contacts the CycT1 Tat-TAR recognition motif (TRM) and the second Tat Zn(2+)-binding loop. Hydrogen-deuterium exchange (HDX) shows that AFF4 helix 2 is stabilized in the TAR complex despite not touching the RNA, explaining how it enhances TAR binding to the SEC 50-fold. RNA SHAPE and SAXS data were used to help model the extended (Tat Arginine-Rich Motif) ARM, which enters the TAR major groove between the bulge and the central loop...
October 12, 2016: ELife
Fabian Mück, Silvia Bracharz, Rolf Marschalek
AF4/AFF1 and AF5/AFF4 are both backbones for the assembly of "super elongation complexes" (SECs) that exert 2 distinct functions after the recruitment of P-TEFb from the 7SK snRNP: (1) initiation and elongation of RNA polymerase II gene transcription, and (2) modification of transcribed gene regions by distinct histone methylation patterns. In this study we aimed to investigate one of the initial steps, namely how P-TEFb is transferred from 7SK snRNPs to the SECs. In particular, we were interested in the role of DDX6 that we have recently identified as part of the AF4 complex...
2016: American Journal of Blood Research
Catherine D Eichhorn, Rahul Chug, Juli Feigon
The 7SK small nuclear ribonucleoprotein (snRNP) sequesters and inactivates the positive transcription elongation factor b (P-TEFb), an essential eukaryotic mRNA transcription factor. The human La-related protein group 7 (hLARP7) is a constitutive component of the 7SK snRNP and localizes to the 3' terminus of the 7SK long noncoding RNA. hLARP7, and in particular its C-terminal domain (CTD), is essential for 7SK RNA stability and assembly with P-TEFb. The hLARP7 N-terminal La module binds and protects the 3' end from degradation, but the structural and functional role of its CTD is unclear...
September 26, 2016: Nucleic Acids Research
Hiroshi Okuda, Satoshi Takahashi, Akifumi Takaori-Kondo, Akihiko Yokoyama
Gene rearrangement of the mixed lineage leukemia (MLL) gene causes leukemia by inducing the constitutive expression of a gene subset normally expressed only in the immature haematopoietic progenitor cells. MLL gene rearrangements often generate fusion products of MLL and a component of the AF4 family/ENL family/P-TEFb (AEP) complex. MLL-AEP fusion proteins have the potential of constitutively recruiting the P-TEFb elongation complex. Thus, it is hypothesized that relieving the promoter proximal pausing of RNA polymerase II is the rate-limiting step of MLL fusion-dependent transcription...
October 17, 2016: Cell Cycle
Yang Zhao, John Karijolich, Britt Glaunsinger, Qiang Zhou
The 7SK snRNA sequesters P-TEFb, a general transcription elongation factor and human co-factor for HIV-1 Tat protein, into the catalytically inactive 7SK snRNP Little is known about how 7SK RNA is regulated to perform this function. Here, we show that most of 7SK is pseudouridylated at position U250 by the predominant cellular pseudouridine synthase machinery, the DKC1-box H/ACA RNP Pseudouridylation is critical to stabilize 7SK snRNP, as its abolishment by either mutation at or around U250 or depletion of DKC1, the catalytic component of the box H/ACA RNP, disrupts 7SK snRNP and releases P-TEFb to form the super elongation complex (SEC) and the Brd4-P-TEFb complex...
October 2016: EMBO Reports
Duchu Chen, Huiping Wang, Jude Juventus Aweya, Yanheng Chen, Meihua Chen, Xiaomeng Wu, Xiaonan Chen, Jing Lu, Ruichuan Chen, Min Liu
In the past decade, much emphasis has been put on the transcriptional activation of HIV-1, which is proposed as a promised strategy for eradicating latent HIV-1 provirus. Two drugs, prostratin and hexamethylene bisacetamide (HMBA), have shown potent effects as inducers for releasing HIV-1 latency when used alone or in combination, although their cellular target(s) are currently not well understood, especially under drug combination. Here, we have shown that HMBA and prostratin synergistically release HIV-1 latency via different mechanisms...
2016: BioMed Research International
Reza K Oqani, Tao Lin, Jae Eun Lee, So Yeon Kim, Soo Jin Sa, Je Seok Woo, Dong Il Jin
Positive transcription elongation factor b (P-TEFb) is an RNA polymerase II kinase that phosphorylates Ser2 of the carboxyl-terminal domain and promotes the elongation phase of transcription. Despite the fact that P-TEFb has role in many cellular processes, the role of this kinase complex remains to be understood in early developmental events. In this study, using immunocytochemical analyses, we find that the P-TEFb components, Cyclin T1, CDK9, and its T-loop phosphorylated form, are localized to nuclear speckles, as well as in nucleoli in mouse germinal vesicle oocytes...
September 2016: Genesis: the Journal of Genetics and Development
Sandeep Rajput, Nimmish Khera, Zhanfang Guo, Jeremy Hoog, Shunqiang Li, Cynthia X Ma
Cyclin-dependent kinases (CDKs) are potential cancer therapeutic targets because of their critical role in promoting cell growth. Dinaciclib is a novel CDK inhibitor currently under clinical evaluation for the treatment of advanced malignancies. In this study, we demonstrated the anti-tumor activity of dinaciclib in triple negative breast cancer (TNBC) patient derived xenograft (PDX) and cell lines in vitro and in vivo. Treatment with dinaciclib induced cell cycle arrest at G2/M phase and marked apoptosis. These changes were accompanied by reduced phosphorylation of CDK1 and retinoblastoma (Rb) protein and decreased protein levels of cyclin B1, cMYC and survivin...
July 28, 2016: Oncotarget
Justyna Zaborowska, Nur F Isa, Shona Murphy
Positive transcription elongation factor b (P-TEFb), which comprises cyclin-dependent kinase 9 (CDK9) kinase and cyclin T subunits, is an essential kinase complex in human cells. Phosphorylation of the negative elongation factors by P-TEFb is required for productive elongation of transcription of protein-coding genes by RNA polymerase II (pol II). In addition, P-TEFb-mediated phosphorylation of the carboxyl-terminal domain (CTD) of the largest subunit of pol II mediates the recruitment of transcription and RNA processing factors during the transcription cycle...
July 2016: BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology
Justyna Zaborowska, Nur F Isa, Shona Murphy
Positive transcription elongation factor b (P-TEFb), which comprises cyclin-dependent kinase 9 (CDK9) kinase and cyclin T subunits, is an essential kinase complex in human cells. Phosphorylation of the negative elongation factors by P-TEFb is required for productive elongation of transcription of protein-coding genes by RNA polymerase II (pol II). In addition, P-TEFb-mediated phosphorylation of the carboxyl-terminal domain (CTD) of the largest subunit of pol II mediates the recruitment of transcription and RNA processing factors during the transcription cycle...
April 2016: Inside the Cell
Alexandre J C Quaresma, Andrii Bugai, Matjaz Barboric
Release of RNA polymerase II (Pol II) from promoter-proximal pausing has emerged as a critical step regulating gene expression in multicellular organisms. The transition of Pol II into productive elongation requires the kinase activity of positive transcription elongation factor b (P-TEFb), which is itself under a stringent control by the inhibitory 7SK small nuclear ribonucleoprotein (7SK snRNP) complex. Here, we provide an overview on stimulating Pol II pause release by P-TEFb and on sequestering P-TEFb into 7SK snRNP...
September 19, 2016: Nucleic Acids Research
Wei Shao, Kristina Zumer, Koh Fujinaga, B Matija Peterlin
The autoimmune regulator (AIRE) is a transcription factor which is expressed in medullary thymic epithelial cells. It directs the expression of otherwise tissue-specific antigens, which leads to the elimination of autoreactive T cells during development. AIRE is modified post-translationally by phosphorylation and ubiquitylation. In this report we connected these modifications. AIRE, which is phosphorylated on two specific residues near its N terminus, then binds to the F-box protein 3 (FBXO3) E3 ubiquitin ligase...
August 19, 2016: Journal of Biological Chemistry
Xiaodong Lu, Xinxing Zhu, You Li, Min Liu, Bin Yu, Yu Wang, Muhua Rao, Haiyang Yang, Kai Zhou, Yao Wang, Yanheng Chen, Meihua Chen, Songkuan Zhuang, Lin-Feng Chen, Runzhong Liu, Ruichuan Chen
The association of DSIF and NELF with initiated RNA Polymerase II (Pol II) is the general mechanism for inducing promoter-proximal pausing of Pol II. However, it remains largely unclear how the paused Pol II is released in response to stimulation. Here, we show that the release of the paused Pol II is cooperatively regulated by multiple P-TEFbs which are recruited by bromodomain-containing protein Brd4 and super elongation complex (SEC) via different recruitment mechanisms. Upon stimulation, Brd4 recruits P-TEFb to Spt5/DSIF via a recruitment pathway consisting of Med1, Med23 and Tat-SF1, whereas SEC recruits P-TEFb to NELF-A and NELF-E via Paf1c and Med26, respectively...
August 19, 2016: Nucleic Acids Research
Victoria L Hatch, Marta Marin-Barba, Simon Moxon, Christopher T Ford, Nicole J Ward, Matthew L Tomlinson, Ines Desanlis, Adam E Hendry, Saartje Hontelez, Ila van Kruijsbergen, Gert Jan C Veenstra, Andrea E Münsterberg, Grant N Wheeler
Regulation of gene expression at the level of transcriptional elongation has been shown to be important in stem cells and tumour cells, but its role in the whole animal is only now being fully explored. Neural crest cells (NCCs) are a multipotent population of cells that migrate during early development from the dorsal neural tube throughout the embryo where they differentiate into a variety of cell types including pigment cells, cranio-facial skeleton and sensory neurons. Specification of NCCs is both spatially and temporally regulated during embryonic development...
August 15, 2016: Developmental Biology
Yingli Shang, Maddalena Coppo, Teng He, Fei Ning, Li Yu, Lan Kang, Bin Zhang, Chanyang Ju, Yu Qiao, Baohong Zhao, Manfred Gessler, Inez Rogatsky, Xiaoyu Hu
Most of the known regulatory mechanisms that curb inflammatory gene expression target pre-transcription-initiation steps, and evidence for post-initiation regulation of inflammatory gene expression remains scarce. We found that the transcriptional repressor Hes1 suppressed production of CXCL1, a chemokine that is crucial for recruiting neutrophils. Hes1 negatively regulated neutrophil recruitment in vivo in a manner that was dependent on macrophage-produced CXCL1, and it attenuated the severity of inflammatory arthritis...
August 2016: Nature Immunology
Qi Xie, Qiulian Wu, Leo Kim, Tyler E Miller, Brian B Liau, Stephen C Mack, Kailin Yang, Daniel C Factor, Xiaoguang Fang, Zhi Huang, Wenchao Zhou, Kareem Alazem, Xiuxing Wang, Bradley E Bernstein, Shideng Bao, Jeremy N Rich
Glioblastomas co-opt stem cell regulatory pathways to maintain brain tumor-initiating cells (BTICs), also known as cancer stem cells. NOTCH signaling has been a molecular target in BTICs, but NOTCH antagonists have demonstrated limited efficacy in clinical trials. Recombining binding protein suppressor of hairless (RBPJ) is considered a central transcriptional mediator of NOTCH activity. Here, we report that pharmacologic NOTCH inhibitors were less effective than targeting RBPJ in suppressing tumor growth. While NOTCH inhibitors decreased canonical NOTCH gene expression, RBPJ regulated a distinct profile of genes critical to BTIC stemness and cell cycle progression...
July 1, 2016: Journal of Clinical Investigation
Arnulf Hertweck, Catherine M Evans, Malihe Eskandarpour, Jonathan C H Lau, Kristine Oleinika, Ian Jackson, Audrey Kelly, John Ambrose, Peter Adamson, David J Cousins, Paul Lavender, Virginia L Calder, Graham M Lord, Richard G Jenner
The transcription factor T-bet directs Th1 cell differentiation, but the molecular mechanisms that underlie this lineage-specific gene regulation are not completely understood. Here, we show that T-bet acts through enhancers to allow the recruitment of Mediator and P-TEFb in the form of the super elongation complex (SEC). Th1 genes are occupied by H3K4me3 and RNA polymerase II in Th2 cells, while T-bet-mediated recruitment of P-TEFb in Th1 cells activates transcriptional elongation. P-TEFb is recruited to both genes and enhancers, where it activates enhancer RNA transcription...
June 21, 2016: Cell Reports
Lien-Fu Lin, Jong-Shiaw Jin, Jui-Chang Chen, Chia-Chi Huang, Jeng-Horng Sheu, Wenlung Chen, Tang-Yi Tsao, Chih-Wei Hsu
Positive transcriptional elongation factor b (P-TEFb) contains the catalytic subunit cyclin-dependent kinase 9 (Cdk9) and the regulatory subunit cyclin T. Cyclin T1 and Cdk9 are the key factors of the PTEFb pathways and are overexpressed in the human head and neck carcinoma cell line. However, there have been limited studies regarding the role of cyclin T1 and Cdk9 in gastric gastrointestinal stromal tumors (GISTs). The aim of the present study was to assess the association between cyclin T1 and Cdk9 and their clinical significance in gastric GISTs...
June 2016: Molecular and Clinical Oncology
Hossein Ghanbarian, Nicole Wagner, Beatrice Polo, Delphine Baudouy, Jafar Kiani, Jean-François Michiels, François Cuzin, Minoo Rassoulzadegan, Kay-Dietrich Wagner
Dnmt2/Trdmt1 is a methyltransferase, which has been shown to methylate tRNAs. Deficient mutants were reported to exhibit various, seemingly unrelated, defects in development and RNA-mediated epigenetic heredity. Here we report a role in a distinct developmental regulation effected by a noncoding RNA. We show that Dnmt2-deficiency in mice results in cardiac hypertrophy. Echocardiographic measurements revealed that cardiac function is preserved notwithstanding the increased dimensions of the organ due to cardiomyocyte enlargement...
2016: PloS One
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