scholarly journals Competition between PAF1 and MLL1/COMPASS confers the opposing function of LEDGF/p75 in HIV latency and proviral reactivation

2020 ◽  
Vol 6 (20) ◽  
pp. eaaz8411
Author(s):  
Ru Gao ◽  
Jiaqian Bao ◽  
Han Yan ◽  
Liya Xie ◽  
Wanchang Qin ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Therapeutic Potential ◽  
Life Cycles ◽  
Elongation Complex ◽  
Hiv Transcription ◽  
Super Elongation Complex ◽  
Replication Control ◽  
Regulatory Functions ◽  
Transcriptional Reactivation ◽  
Hiv Integration

Transcriptional status determines the HIV replicative state in infected patients. However, the transcriptional mechanisms for proviral replication control remain unclear. In this study, we show that, apart from its function in HIV integration, LEDGF/p75 differentially regulates HIV transcription in latency and proviral reactivation. During latency, LEDGF/p75 suppresses proviral transcription via promoter-proximal pausing of RNA polymerase II (Pol II) by recruiting PAF1 complex to the provirus. Following latency reversal, MLL1 complex competitively displaces PAF1 from the provirus through casein kinase II (CKII)–dependent association with LEDGF/p75. Depleting or pharmacologically inhibiting CKII prevents PAF1 dissociation and abrogates the recruitment of both MLL1 and Super Elongation Complex (SEC) to the provirus, thereby impairing transcriptional reactivation for latency reversal. These findings, therefore, provide a mechanistic understanding of how LEDGF/p75 coordinates its distinct regulatory functions at different stages of the post-integrated HIV life cycles. Targeting these mechanisms may have a therapeutic potential to eradicate HIV infection.

Allosteric transcription stimulation by RNA polymerase II super elongation complex

2021 ◽  
Author(s):  
Ying Chen ◽  
Seychelle M. Vos ◽  
Christian Dienemann ◽  
Momchil Ninov ◽  
Henning Urlaub ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Elongation Complex ◽  
Super Elongation Complex

scholarly journals Super elongation complex as a targetable dependency in diffuse midline glioma

2020 ◽  
Author(s):  
Nathan A. Dahl ◽  
Etienne Danis ◽  
Ilango Balakrishnan ◽  
Dong Wang ◽  
Angela Pierce ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Elongation Complex ◽  
Curative Therapy ◽  
Super Elongation Complex ◽  
Small Molecule Inhibition ◽  
Promising Therapeutic Approach ◽  
Clonogenic Potential ◽  
Diffuse Intrinsic Pontine Gliomas ◽  
Shrna Screen

AbstractMutations in the histone 3 gene (H3K27M) are the eponymous drivers in diffuse intrinsic pontine gliomas (DIPGs) and other diffuse midline gliomas (DMGs), aggressive pediatric brain cancers for which no curative therapy currently exists. The salient molecular consequence of these recurrent oncohistones is a global loss of repressive H3K27me3 residues and broad epigenetic dysregulation. In order to identify specific, therapeutically targetable epigenetic dependencies within this disease context, we performed an shRNA screen targeting 408 genes classified as epigenetic/chromatin-associated molecules in patient-derived DMG cultures. This approach identified AFF4, the scaffold protein of the super elongation complex (SEC), as a previously-undescribed dependency in DMG. Interrogation of SEC function demonstrated a key role for maintaining DMG cell viability and clonogenic potential while promoting self-renewal of DMG tumor stem cells. Small-molecule inhibition of the SEC with the highly-specific, clinically relevant CDK9 inhibitors atuveciclib and AZD4573 restores regulatory RNA polymerase II pausing, promotes cellular differentiation, and leads to potent anti-tumor effect both in vitro and in patient-derived xenograft models. These studies present a biologic rationale for translational exploration of CDK9 inhibition as a promising therapeutic approach in a disease which currently has no effective medical therapies.

scholarly journals ENL initiates multivalent phase separation of the super elongation complex (SEC) in controlling rapid transcriptional activation

2020 ◽  
Vol 6 (14) ◽  
pp. eaay4858 ◽  
Author(s):  
Chenghao Guo ◽  
Zhuanzhuan Che ◽  
Junjie Yue ◽  
Peng Xie ◽  
Shaohua Hao ◽  
...  
Keyword(s):  
Phase Separation ◽  
Rna Polymerase Ii ◽  
Transcriptional Activation ◽  
Liquid Droplet ◽  
Critical Role ◽  
Elongation Factor ◽  
Elongation Complex ◽  
Intrinsically Disordered ◽  
Super Elongation Complex

Release of paused RNA polymerase II (Pol II) requires incorporation of the positive transcription elongation factor b (P-TEFb) into the super elongation complex (SEC), thus resulting in rapid yet synchronous transcriptional activation. However, the mechanism underlying dynamic transition of P-TEFb from inactive to active state remains unclear. Here, we found that the SEC components are able to compartmentalize and concentrate P-TEFb via liquid-liquid phase separation from the soluble inactive HEXIM1 containing the P-TEFb complex. Specifically, ENL or its intrinsically disordered region is sufficient to initiate the liquid droplet formation of SEC. AFF4 functions together with ENL in fluidizing SEC droplets. SEC droplets are fast and dynamically formed upon serum exposure and required for rapid transcriptional induction. We also found that the fusion of ENL with MLL can boost SEC phase separation. In summary, our results suggest a critical role of multivalent phase separation of SEC in controlling transcriptional pause release.

scholarly journals Super elongation complex promotes early HIV transcription and its function is modulated by P-TEFb

Transcription ◽  
2017 ◽  
Vol 8 (3) ◽  
pp. 133-149 ◽  
Author(s):  
Alona Kuzmina ◽  
Simona Krasnopolsky ◽  
Ran Taube
Keyword(s):  
Elongation Complex ◽  
Hiv Transcription ◽  
Super Elongation Complex

scholarly journals DIPG-34. SUPER ELONGATION COMPLEX AS A TARGETABLE DEPENDENCY IN H3K27M+ DIFFUSE MIDLINE GLIOMA

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii293-iii293
Author(s):  
Nathan Dahl ◽  
Etienne Danis ◽  
Ilango Balakrishnan ◽  
Dong Wang ◽  
Angela Pierce ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Gene Set Enrichment Analysis ◽  
Regulatory Control ◽  
Elongation Complex ◽  
Self Renewal ◽  
Curative Therapy ◽  
Super Elongation Complex ◽  
Promising Therapeutic Approach ◽  
H3k27m Mutation

Abstract Mutations in the histone 3 gene (H3K27M) are the eponymous driver in diffuse intrinsic pontine gliomas (DIPGs) and other diffuse midline gliomas (DMGs), aggressive pediatric brain tumors for which no curative therapy currently exists. To identify specific epigenetic dependencies within the context of the H3K27M mutation, we performed an shRNA screen targeting 408 genes classified as epigenetic/chromatin-associated molecules in patient-derived DMG cultures. This identified AFF4, a component of the super elongation complex (SEC), as necessary for DMG cells to maintain growth and self-renewal. We hypothesized that aberrant SEC expression occurs as a consequence of the H3K27M mutation and that this dysregulated SEC signaling overcomes repressive transcriptional regulation in order to suppresses differentiation and promote self-renewal of DMG tumor stem cells. We interrogated the role of AFF4 in DMG using an shRNA lentiviral approach. We demonstrate a significant decrease in in vitro clonogenicity and stem cell maintenance following AFF4 depletion. We employed RNA-seq-based gene set enrichment analysis to delineate differentiation programs under SEC regulatory control. Finally, we sought to determine whether CDK9, the catalytic subunit of the SEC, represents a therapeutic vulnerability in DMG. Using RNA polymerase II ChIP-seq, we demonstrate that CDK9 pharmacologic inhibition restores regulatory Pol II pausing, promotes cellular differentiation, and leads to potent anti-tumor effect both in vitro and in patient-derived xenograft models. These studies present a biologic rationale for the translational exploration of CDK9 inhibition as a promising therapeutic approach.

scholarly journals Structural mechanism for HIV-1 TAR loop recognition by Tat and the super elongation complex

2018 ◽  
Vol 115 (51) ◽  
pp. 12973-12978 ◽  
Author(s):  
Ursula Schulze-Gahmen ◽  
James H. Hurley
Keyword(s):  
Rna Polymerase Ii ◽  
Binding Affinity ◽  
Electrostatic Interactions ◽  
Mutational Analysis ◽  
Side Chains ◽  
Elongation Complex ◽  
Pol Ii ◽  
Structural Mechanism ◽  
Super Elongation Complex ◽  
Hiv 1

Promoter-proximal pausing by RNA polymerase II (Pol II) is a key regulatory step in human immunodeficiency virus-1 (HIV-1) transcription and thus in the reversal of HIV latency. By binding to the nascent transactivating response region (TAR) RNA, HIV-1 Tat recruits the human super elongation complex (SEC) to the promoter and releases paused Pol II. Structural studies of TAR interactions have been largely focused on interactions between the TAR bulge and the arginine-rich motif (ARM) of Tat. Here, the crystal structure of the TAR loop in complex with Tat and the SEC core was determined at a 3.5-Å resolution. The bound TAR loop is stabilized by cross-loop hydrogen bonds. It makes structure-specific contacts with the side chains of the Cyclin T1 Tat-TAR recognition motif (TRM) and the zinc-coordinating loop of Tat. The TAR loop phosphate backbone forms electrostatic and VDW interactions with positively charged side chains of the CycT1 TRM. Mutational analysis showed that these interactions contribute importantly to binding affinity. The Tat ARM was present in the crystallized construct; however, it was not visualized in the electron density, and the TAR bulge was not formed in the RNA construct used in crystallization. Binding assays showed that TAR bulge-Tat ARM interactions contribute less to TAR binding affinity than TAR loop interactions with the CycT1 TRM and Tat core. Thus, the TAR loop evolved to make high-affinity interactions with the TRM while Tat has three roles: scaffolding and stabilizing the TRM, making specific interactions through its zinc-coordinating loop, and making electrostatic interactions through its ARM.

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