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https://www.readbyqxmd.com/read/27865805/transcriptional-activation-by-mll-fusion-proteins-in-leukemogenesis
#1
REVIEW
Akihiko Yokoyama
Chromosomal translocations involving the mixed lineage leukemia (MLL) gene cause aggressive leukemia. Fusion proteins of MLL and a component of the AF4 family/ENL family/P-TEFb complex (AEP) are responsible for two-thirds of MLL-associated leukemia cases. MLL-AEP fusion proteins trigger aberrant self-renewal of hematopoietic progenitors by constitutively activating self-renewal-related genes. MLL-AEP fusion proteins activate transcription initiation by loading the TATA-binding protein (TBP) to the TATA element via selectivity factor 1...
November 16, 2016: Experimental Hematology
https://www.readbyqxmd.com/read/27863397/targeting-gli-by-gant61-involves-mechanisms-dependent-on-inhibition-of-both-transcription-and-dna-licensing
#2
Ruowen Zhang, Jiahui Wu, Sylvain Ferrandon, Katie J Glowacki, Janet A Houghton
The GLI genes are transcription factors and in cancers are oncogenes, aberrantly and constitutively activated. GANT61, a specific GLI inhibitor, has induced extensive cytotoxicity in human models of colon cancer. The FOXM1 promoter was determined to be a transcriptional target of GLI1. In HT29 cells, inhibition of GLI1 binding at the GLI consensus sequence by GANT61 led to inhibited binding of Pol II, the pause-release factors DSIF, NELF and p-TEFb. The formation of R-loops (RNA:DNA hybrids, ssDNA), were reduced by GANT61 at the FOXM1 promoter...
November 15, 2016: Oncotarget
https://www.readbyqxmd.com/read/27852926/solution-structure-of-the-5-terminal-hairpin-of-the-7sk-small-nuclear-rna
#3
Sarah Bourbigot, Anne-Catherine Dock-Bregeon, Pascal Eberling, Jérôme Coutant, Bruno Kieffer, Isabelle Lebars
The small nuclear 7SK RNA regulates RNA polymerase II (RNA Pol II) transcription, by sequestering and inhibiting the positive transcription elongation factor b (P-TEFb). P-TEFb is stored in the 7SK ribonucleoprotein (RNP) that contains the three nuclear proteins Hexim1, LaRP7, and MePCE. P-TEFb interacts with the protein Hexim1 and the 7SK RNA. Once P-TEFb is released from the 7SK RNP, it activates transcription by phosphorylating the C-terminal domain of RNA Pol II. P-TEFb also plays a crucial role in the replication of the human immunodeficiency virus HIV-1, through its recruitment by the viral transactivator Tat...
December 2016: RNA
https://www.readbyqxmd.com/read/27833949/the-emerging-picture-of-cdk9-p-tefb-more-than-20-years-of-advances-since-pitalre
#4
REVIEW
Nikolas Ferreira Dos Santos Paparidis, Maxwell Castro Durvale, Fernanda Canduri
CDK9 is a prominent member of the transcriptional CDKs subfamily, a group of kinases whose function is to control the primary steps of mRNA synthesis and processing by eukaryotic RNA polymerase II. As a cyclin-dependent kinase, CDK9 activation in vivo depends upon its association with T-type cyclins to assemble the positive transcription elongation factor (P-TEFb). Although CDK9/P-TEFb phosphorylates the C-terminal domain of RNAP II in the same positions targeted by CDK7 (TFIIH) and CDK8 (Mediator), the former does not participate in the transcription initiation, but rather plays a unique role by driving the polymerase to productive elongation...
November 11, 2016: Molecular BioSystems
https://www.readbyqxmd.com/read/27799305/heat-shock-protein-90-facilitates-latent-hiv-reactivation-through-maintaining-the-function-of-positive-transcriptional-elongation-factor-b-p-tefb-under-proteasome-inhibition
#5
Xiao-Yan Pan, Wei Zhao, Chun-Yan Wang, Jian Lin, Xiao-Yun Zeng, Ru-Xia Ren, Keng Wang, Tian-Rong Xun, Yechiel Shai, Shu-Wen Liu
The persistence of HIV in resting memory CD4+ T cells at a latent state is considered as the major barrier on the path to achieve a cure for HIV. Proteasome inhibitors (PIs) were previously reported as latency reversing agents (LRAs) but the mechanism underlying this function is yet unclear. Here we demonstrate that PIs reactivate latent HIV ex vivo without global T cell activation, and may facilitate host innate immune responses. Mechanistically, latent HIV reactivation induced by PIs is mediated by heat shock factor 1 (HSF1) via the recruitment of the heat shock protein (HSP) 90-positive transcriptional elongation factor b (p-TEFb) complex...
October 31, 2016: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/27791144/an-evolutionary-conserved-hexim1-peptide-binds-to-the-cdk9-catalytic-site-to-inhibit-p-tefb
#6
Lydia Kobbi, Emmanuelle Demey-Thomas, Floriane Braye, Florence Proux, Olga Kolesnikova, Joelle Vinh, Arnaud Poterszman, Olivier Bensaude
The positive transcription elongation factor (P-TEFb) is required for the transcription of most genes by RNA polymerase II. Hexim proteins associated with 7SK RNA bind to P-TEFb and reversibly inhibit its activity. P-TEFb comprises the Cdk9 cyclin-dependent kinase and a cyclin T. Hexim proteins have been shown to bind the cyclin T subunit of P-TEFb. How this binding leads to inhibition of the kinase activity of Cdk9 has remained elusive, however. Using a photoreactive amino acid incorporated into proteins, we show that in live cells, cell extracts, and in vitro reconstituted complexes, Hexim1 cross-links and thus contacts Cdk9...
October 25, 2016: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/27771926/potential-use-of-flavopiridol-in-treatment-of-chronic-diseases
#7
Thejal Srikumar, Jaya Padmanabhan
This chapter describes the potential use of flavopiridol, a CDK inhibitor with anti-inflammatory and anti-proliferative activities, in the treatment of various chronic diseases. Flavopiridol arrests cell cycle progression in the G1 or G2 phase by inhibiting the kinase activities of CDK1, CDK2, CDK4/6, and CDK7. Additionally, it binds tightly to CDK9, a component of the P-TEFb complex (CDK9/cyclin T), and interferes with RNA polymerase II activation and associated transcription. This in turn inhibits expression of several pro-survival and anti-apoptotic genes, and enhances cytotoxicity in transformed cells or differentiation in growth-arrested cells...
2016: Advances in Experimental Medicine and Biology
https://www.readbyqxmd.com/read/27764245/an-epigenetic-compound-library-screen-identifies-bet-inhibitors-that-promote-hsv-1-and-2-replication-by-bridging-p-tefb-to-viral-gene-promoters-through-brd4
#8
Ke Ren, Wei Zhang, Xiaoqing Chen, Yingyu Ma, Yue Dai, Yimei Fan, Yayi Hou, Ren Xiang Tan, Erguang Li
The human HSV-1 and -2 are common pathogens of human diseases. Both host and viral factors are involved in HSV lytic infection, although detailed mechanisms remain elusive. By screening a chemical library of epigenetic regulation, we identified bromodomain-containing protein 4 (BRD4) as a critical player in HSV infection. We show that treatment with pan BD domain inhibitor enhanced both HSV infection. Using JQ1 as a probe, we found that JQ1, a defined BD1 inhibitor, acts through BRD4 protein since knockdown of BRD4 expression ablated JQ1 effect on HSV infection...
October 2016: PLoS Pathogens
https://www.readbyqxmd.com/read/27752877/7sk-small-nuclear-rna-transcription-level-down-regulates-in-human-tumors-and-stem-cells
#9
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
https://www.readbyqxmd.com/read/27731797/insights-into-hiv-1-proviral-transcription-from-integrative-structure-and-dynamics-of-the-tat-aff4-p-tefb-tar-complex
#10
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
https://www.readbyqxmd.com/read/27679741/ddx6-transfers-p-tefb-kinase-to-the-af4-af4n-aff1-super-elongation-complex
#11
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
https://www.readbyqxmd.com/read/27679474/hlarp7-c-terminal-domain-contains-an-xrrm-that-binds-the-3-hairpin-of-7sk-rna
#12
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...
November 16, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27564129/tbp-loading-by-af4-through-sl1-is-the-major-rate-limiting-step-in-mll-fusion-dependent-transcription
#13
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
https://www.readbyqxmd.com/read/27558685/pseudouridylation-of-7sk-snrna-promotes-7sk-snrnp-formation-to-suppress-hiv-1-transcription-and-escape-from-latency
#14
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
https://www.readbyqxmd.com/read/27529070/hmba-enhances-prostratin-induced-activation-of-latent-hiv-1-via-suppressing-the-expression-of-negative-feedback-regulator-a20-tnfaip3-in-nf-%C3%AE%C2%BAb-signaling
#15
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
https://www.readbyqxmd.com/read/27488304/inhibition-of-p-tefb-disrupts-global-transcription-oocyte-maturation-and-embryo-development-in-the-mouse
#16
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
https://www.readbyqxmd.com/read/27486754/inhibition-of-cyclin-dependent-kinase-9-by-dinaciclib-suppresses-cyclin-b1-expression-and-tumor-growth-in-triple-negative-breast-cancer
#17
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
https://www.readbyqxmd.com/read/27417125/p-tefb-goes-viral
#18
REVIEW
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
https://www.readbyqxmd.com/read/27398404/p-tefb-goes-viral
#19
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
https://www.readbyqxmd.com/read/27369380/cracking-the-control-of-rna-polymerase-ii-elongation-by-7sk-snrnp-and-p-tefb
#20
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
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