scholarly journals Brd4 and HEXIM1: Multiple Roles in P-TEFb Regulation and Cancer

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Ruichuan Chen ◽  
Jasper H. N. Yik ◽  
Qiao Jing Lew ◽  
Sheng-Hao Chao
Keyword(s):  
Rna Polymerase Ii ◽  
Cell Cycle Progression ◽  
Current Knowledge ◽  
Elongation Factor ◽  
Multiple Roles ◽  
Transcriptional Elongation ◽  
Small Nuclear Rna ◽  
Cycle Progression ◽  
Hexamethylene Bisacetamide ◽  
Inducible Protein

Bromodomain-containing protein 4 (Brd4) and hexamethylene bisacetamide (HMBA) inducible protein 1 (HEXIM1) are two opposing regulators of the positive transcription elongation factor b (P-TEFb), which is the master modulator of RNA polymerase II during transcriptional elongation. While Brd4 recruits P-TEFb to promoter-proximal chromatins to activate transcription, HEXIM1 sequesters P-TEFb into an inactive complex containing the 7SK small nuclear RNA. Besides regulating P-TEFb’s transcriptional activity, recent evidence demonstrates that both Brd4 and HEXIM1 also play novel roles in cell cycle progression and tumorigenesis. Here we will discuss the current knowledge on Brd4 and HEXIM1 and their implication as novel therapeutic options against cancer.

scholarly journals The Multiple Roles of the Cdc14 Phosphatase in Cell Cycle Control

2020 ◽  
Vol 21 (3) ◽  
pp. 709
Author(s):  
Javier Manzano-López ◽  
Fernando Monje-Casas
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Current Knowledge ◽  
Cell Cycle Control ◽  
Multiple Roles ◽  
Special Focus ◽  
Cyclin Dependent Kinase ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cycle Progression

The Cdc14 phosphatase is a key regulator of mitosis in the budding yeast Saccharomyces cerevisiae. Cdc14 was initially described as playing an essential role in the control of cell cycle progression by promoting mitotic exit on the basis of its capacity to counteract the activity of the cyclin-dependent kinase Cdc28/Cdk1. A compiling body of evidence, however, has later demonstrated that this phosphatase plays other multiple roles in the regulation of mitosis at different cell cycle stages. Here, we summarize our current knowledge about the pivotal role of Cdc14 in cell cycle control, with a special focus in the most recently uncovered functions of the phosphatase.

scholarly journals The Yin and Yang of P-TEFb Regulation: Implications for Human Immunodeficiency Virus Gene Expression and Global Control of Cell Growth and Differentiation

2006 ◽  
Vol 70 (3) ◽  
pp. 646-659 ◽  
Author(s):  
Qiang Zhou ◽  
Jasper H. N. Yik
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase Ii ◽  
Elongation Factor ◽  
Transcriptional Elongation ◽  
Small Nuclear Rna ◽  
Cellular Genes ◽  
Immunodeficiency Virus ◽  
Cellular Cofactor ◽  
Cell Growth And Differentiation ◽  
Carboxy Terminal

SUMMARY The positive transcription elongation factor b (P-TEFb) stimulates transcriptional elongation by phosphorylating the carboxy-terminal domain of RNA polymerase II and antagonizing the effects of negative elongation factors. Not only is P-TEFb essential for transcription of the vast majority of cellular genes, but it is also a critical host cellular cofactor for the expression of the human immunodeficiency virus (HIV) type 1 genome. Given its important role in globally affecting transcription, P-TEFb's activity is dynamically controlled by both positive and negative regulators in order to achieve a functional equilibrium in sync with the overall transcriptional demand as well as the proliferative state of cells. Notably, this equilibrium can be shifted toward either the active or inactive state in response to diverse physiological stimuli that can ultimately affect the cellular decision between growth and differentiation. In this review, we examine the mechanisms by which the recently identified positive (the bromodomain protein Brd4) and negative (the noncoding 7SK small nuclear RNA and the HEXIM1 protein) regulators of P-TEFb affect the P-TEFb-dependent transcriptional elongation. We also discuss the consequences of perturbations of the dynamic associations of these regulators with P-TEFb in relation to the pathogenesis and progression of several major human diseases, such as cardiac hypertrophy, breast cancer, and HIV infection.

scholarly journals MAQ1 and 7SK RNA Interact with CDK9/Cyclin T Complexes in a Transcription-Dependent Manner

2003 ◽  
Vol 23 (14) ◽  
pp. 4859-4869 ◽  
Author(s):  
Annemieke A. Michels ◽  
Van Trung Nguyen ◽  
Alessandro Fraldi ◽  
Valérie Labas ◽  
Mia Edwards ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Specific Interaction ◽  
Elongation Factor ◽  
Virus Genome ◽  
Transcriptional Elongation ◽  
Dependent Manner ◽  
Small Nuclear Rna ◽  
Cyclin T1 ◽  
Terminal Domain ◽  
Immunodeficiency Virus

ABSTRACT Positive transcription elongation factor b (P-TEFb) comprises a cyclin (T1 or T2) and a kinase, cyclin-dependent kinase 9 (CDK9), which phosphorylates the carboxyl-terminal domain of RNA polymerase II. P-TEFb is essential for transcriptional elongation in human cells. A highly specific interaction among cyclin T1, the viral protein Tat, and the transactivation response (TAR) element RNA determines the productive transcription of the human immunodeficiency virus genome. In growing HeLa cells, half of P-TEFb is kinase inactive and binds to the 7SK small nuclear RNA. We now report on a novel protein termed MAQ1 (for ménage à quatre) that is also present in this complex. Since 7SK RNA is required for MAQ1 to associate with P-TEFb, a structural role for 7SK RNA is proposed. Inhibition of transcription results in the release of both MAQ1 and 7SK RNA from P-TEFb. Thus, MAQ1 cooperates with 7SK RNA to form a novel type of CDK inhibitor. According to yeast two-hybrid analysis and immunoprecipitations from extracts of transfected cells, MAQ1 binds directly to the N-terminal cyclin homology region of cyclins T1 and T2. Since Tat also binds to this cyclin T1 N-terminal domain and since the association between 7SK RNA/MAQ1 and P-TEFb competes with the binding of Tat to cyclin T1, we speculate that the TAR RNA/Tat lentivirus system has evolved to subvert the cellular 7SK RNA/MAQ1 system.

Downregulation of Dihydrotestosterone and Estradiol Levels by HEXIM1

Endocrinology ◽  
2021 ◽  
Vol 163 (1) ◽  
Author(s):  
Fitya Mozar ◽  
Vikas Sharma ◽  
Shashank Gorityala ◽  
Jeffrey M Albert ◽  
Yan Xu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Proliferation ◽  
Rna Polymerase Ii ◽  
Transcriptional Activity ◽  
Elongation Factor ◽  
Estrogen Receptor Α ◽  
Transcriptional Elongation ◽  
Key Enzyme ◽  
Functional Consequences ◽  
Inducible Protein

Abstract We have previously reported that hexamethylene bis-acetamide inducible protein 1 (HEXIM1) inhibits the activity of ligand-bound estrogen receptor α (ERα) and the androgen receptor (AR) by disrupting the interaction between these receptors and positive transcriptional elongation factor b (P-TEFb) and attenuating RNA polymerase II (RNAPII) phosphorylation at serine 2. Functional consequences of the inhibition of transcriptional activity of ERα and AR by HEXIM1 include the inhibition of ERα- and AR-dependent gene expression, respectively, and the resulting attenuation of breast cancer (BCa) and prostate cancer (PCa) cell proliferation and growth. In our present study, we determined that HEXIM1 inhibited AKR1C3 expression in BCa and PCa cells. AKR1C3, also known as 17β-hydroxysteroid dehydrogenase (17β-HSD) type 5, is a key enzyme involved in the synthesis of 17β-estradiol (E2) and 5-dihydrotestosterone (DHT). Downregulation of AKR1C3 by HEXIM1 influenced E2 and DHT production, estrogen- and androgen-dependent gene expression, and cell proliferation. Our studies indicate that HEXIM1 has the unique ability to inhibit both the transcriptional activity of the ER and AR and the synthesis of the endogenous ligands of these receptors.

scholarly journals Brd4 Recruits P-TEFb to Chromosomes at Late Mitosis To Promote G1 Gene Expression and Cell Cycle Progression

2007 ◽  
Vol 28 (3) ◽  
pp. 967-976 ◽  
Author(s):  
Zhiyuan Yang ◽  
Nanhai He ◽  
Qiang Zhou
Keyword(s):  
Cell Cycle ◽  
Rna Polymerase Ii ◽  
Cell Cycle Progression ◽  
Transcriptional Elongation ◽  
Cycle Progression ◽  
Cyclin T1 ◽  
General Transcription Factors ◽  
Cycle Arrest ◽  
Active Transcription ◽  
Late Mitosis

ABSTRACT Brd4, a bromodomain protein capable of interacting with acetylated histones, is implicated in transmitting epigenetic memory through mitosis. It also functions as an associated factor and positive regulator of P-TEFb, a Cdk9-cyclin T1 heterodimer that stimulates transcriptional elongation by phosphorylating RNA polymerase II. In the present study, experiments were performed to determine whether these two functions of Brd4 are interrelated and, if so, how they may impact cell cycle progression. Our data demonstrate that while the P-TEFb level remains constant, the Brd4-P-TEFb interaction increases dramatically in cells progressing from late mitosis to early G1. Concurrently, P-TEFb is recruited to chromosomes, beginning around mid- to late anaphase and before nuclear envelope/lamina formation and nuclear import of other general transcription factors. Importantly, the recruitment of P-TEFb depends on Brd4. Abrogation of this process through Brd4 knockdown reduces the binding of P-TEFb to and expression of key G1 and growth-associated genes, leading to G1 cell cycle arrest and apoptosis. Because P-TEFb is synonymous with productive elongation, its recruitment by Brd4 to chromosomes at late mitosis may indicate those genes whose active transcription status must be preserved across cell division.

scholarly journals Regulation of P-TEFb Elongation Complex Activity by CDK9 Acetylation

2007 ◽  
Vol 27 (13) ◽  
pp. 4641-4651 ◽  
Author(s):  
Junjiang Fu ◽  
Ho-Geun Yoon ◽  
Jun Qin ◽  
Jiemin Wong
Keyword(s):  
Rna Polymerase Ii ◽  
Elongation Factor ◽  
Transcriptional Elongation ◽  
Elongation Complex ◽  
Complex Activity ◽  
Interacting Protein ◽  
Pol Ii ◽  
Carboxy Terminal

ABSTRACT P-TEFb, comprised of CDK9 and a cyclin T subunit, is a global transcriptional elongation factor important for most RNA polymerase II (pol II) transcription. P-TEFb facilitates transcription elongation in part by phosphorylating Ser2 of the heptapeptide repeat of the carboxy-terminal domain (CTD) of the largest subunit of pol II. Previous studies have shown that P-TEFb is subjected to negative regulation by forming an inactive complex with 7SK small RNA and HEXIM1. In an effort to investigate the molecular mechanism by which corepressor N-CoR mediates transcription repression, we identified HEXIM1 as an N-CoR-interacting protein. This finding led us to test whether the P-TEFb complex is regulated by acetylation. We demonstrate that CDK9 is an acetylated protein in cells and can be acetylated by p300 in vitro. Through both in vitro and in vivo assays, we identified lysine 44 of CDK9 as a major acetylation site. We present evidence that CDK9 is regulated by N-CoR and its associated HDAC3 and that acetylation of CDK9 affects its ability to phosphorylate the CTD of pol II. These results suggest that acetylation of CDK9 is an important posttranslational modification that is involved in regulating P-TEFb transcriptional elongation function.

Identification of rpo30, a vaccinia virus RNA polymerase gene with structural similarity to a eucaryotic transcription elongation factor

1990 ◽  
Vol 10 (10) ◽  
pp. 5433-5441
Author(s):  
B Y Ahn ◽  
P D Gershon ◽  
E V Jones ◽  
B Moss
Keyword(s):  
Rna Polymerase ◽  
Vaccinia Virus ◽  
Rna Polymerase Ii ◽  
Elongation Factor ◽  
Viral Rna ◽  
In Vitro Translation ◽  
Virus Protein ◽  
Transcriptional Elongation

Eucaryotic transcription factors that stimulate RNA polymerase II by increasing the efficiency of elongation of specifically or randomly initiated RNA chains have been isolated and characterized. We have identified a 30-kilodalton (kDa) vaccinia virus-encoded protein with apparent homology to SII, a 34-kDa mammalian transcriptional elongation factor. In addition to amino acid sequence similarities, both proteins contain C-terminal putative zinc finger domains. Identification of the gene, rpo30, encoding the vaccinia virus protein was achieved by using antibody to the purified viral RNA polymerase for immunoprecipitation of the in vitro translation products of in vivo-synthesized early mRNA selected by hybridization to cloned DNA fragments of the viral genome. Western immunoblot analysis using antiserum made to the vaccinia rpo30 protein expressed in bacteria indicated that the 30-kDa protein remains associated with highly purified viral RNA polymerase. Thus, the vaccinia virus protein, unlike its eucaryotic homolog, is an integral RNA polymerase subunit rather than a readily separable transcription factor. Further studies showed that the expression of rpo30 is regulated by dual early and later promoters.

scholarly journals Mutagenesis of ARS2 Domains To Assess Possible Roles in Cell Cycle Progression and MicroRNA and Replication-Dependent Histone mRNA Biogenesis

2015 ◽  
Vol 35 (21) ◽  
pp. 3753-3767 ◽  
Author(s):  
Connor O'Sullivan ◽  
Jennifer Christie ◽  
Marcus Pienaar ◽  
Jake Gambling ◽  
Philip E. B. Nickerson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Rna Polymerase Ii ◽  
Cell Cycle Progression ◽  
Rna Recognition Motif ◽  
Rna Recognition ◽  
Histone Mrna ◽  
Cycle Progression ◽  
Transcript Processing ◽  
C Terminus ◽  
Domain Of Unknown Function

ARS2 is a regulator of RNA polymerase II transcript processing through its role in the maturation of distinct nuclear cap-binding complex (CBC)-controlled RNA families. In this study, we examined ARS2 domain function in transcript processing. Structural modeling based on the plant ARS2 orthologue, SERRATE, revealed 2 previously uncharacterized domains in mammalian ARS2: an N-terminal domain of unknown function (DUF3546), which is also present in SERRATE, and an RNA recognition motif (RRM) that is present in metazoan ARS2 but not in plants. Both the DUF3546 and zinc finger domain (ZnF) were required for association with microRNA and replication-dependent histone mRNA. Mutations in the ZnF disrupted interaction with FLASH, a key component in histone pre-mRNA processing. Mutations targeting the Mid domain implicated it in DROSHA interaction and microRNA biogenesis. The unstructured C terminus was required for interaction with the CBC protein CBP20, while the RRM was required for cell cycle progression and for binding to FLASH. Together, our results support a bridging model in which ARS2 plays a central role in RNA recognition and processing through multiple protein and RNA interactions.

scholarly journals Mechanotransduction via the LINC complex regulates DNA replication in myonuclei

2018 ◽  
Vol 217 (6) ◽  
pp. 2005-2018 ◽  
Author(s):  
Shuoshuo Wang ◽  
Elizabeth Stoops ◽  
Unnikannan CP ◽  
Barak Markus ◽  
Adriana Reuveny ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Dna Content ◽  
Cell Cycle Progression ◽  
Mechanical Stimuli ◽  
Linc Complex ◽  
Cycle Progression ◽  
Binding Profile ◽  
Genome Wide ◽  
Chromatin Regulator ◽  
Dna Endoreplication

Nuclear mechanotransduction has been implicated in the control of chromatin organization; however, its impact on functional contractile myofibers is unclear. We found that deleting components of the linker of nucleoskeleton and cytoskeleton (LINC) complex in Drosophila melanogaster larval muscles abolishes the controlled and synchronized DNA endoreplication, typical of nuclei across myofibers, resulting in increased and variable DNA content in myonuclei of individual myofibers. Moreover, perturbation of LINC-independent mechanical input after knockdown of β-Integrin in larval muscles similarly led to increased DNA content in myonuclei. Genome-wide RNA-polymerase II occupancy analysis in myofibers of the LINC mutant klar indicated an altered binding profile, including a significant decrease in the chromatin regulator barrier-to-autointegration factor (BAF) and the contractile regulator Troponin C. Importantly, muscle-specific knockdown of BAF led to increased DNA content in myonuclei, phenocopying the LINC mutant phenotype. We propose that mechanical stimuli transmitted via the LINC complex act via BAF to regulate synchronized cell-cycle progression of myonuclei across single myofibers.

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