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  1. Article ; Online: 7SK RNA, a non-coding RNA regulating P-TEFb, a general transcription factor.

    Diribarne, Gaelle / Bensaude, Olivier

    RNA biology

    2009  Volume 6, Issue 2, Page(s) 122–128

    Abstract: Human 7SK RNA is an abundant 331 nt nuclear transcript generated by RNA polymerase III. Binding of 7SK RNA to HEXIM1/2 turns these proteins into inhibitors of P-TEFb (Positive Transcriptional Elongation Factor b). P-TEFb is required for RNA polymerase II ...

    Abstract Human 7SK RNA is an abundant 331 nt nuclear transcript generated by RNA polymerase III. Binding of 7SK RNA to HEXIM1/2 turns these proteins into inhibitors of P-TEFb (Positive Transcriptional Elongation Factor b). P-TEFb is required for RNA polymerase II transcription elongation. 7SK RNA is released from P-TEFb/HEXIM/7SK complexes upon an arrest in transcription and physiological stimulations such as cardiac hypertrophy, leading to P-TEFb activation. The released 7SK RNA associates a subset of heterogeneous nuclear ribonucleoproteins (hnRNP). 7SK RNA has been evolutionary conserved in vertebrates and homologues are found in annelid, mollusc and insect genomes. 7SK RNA folds into several hairpins that serve as specific platforms for binding proteins. It is stabilized by mono-methylation of its 5'-triphosphate group and binding of a specific La-Related protein, LARP7 at its 3' end. As the likely best characterized example, 7SK RNA is a paradigm for non-coding RNAs regulating transcription.
    MeSH term(s) Base Sequence ; Humans ; Molecular Sequence Data ; Nucleic Acid Conformation ; Positive Transcriptional Elongation Factor B/genetics ; RNA, Messenger/genetics ; RNA, Small Nuclear/genetics ; RNA, Untranslated/genetics ; RNA, Untranslated/physiology ; Ribonucleoproteins/genetics ; Transcription, Genetic/physiology
    Chemical Substances Larp7 protein, human ; RNA, Messenger ; RNA, Small Nuclear ; RNA, Untranslated ; Ribonucleoproteins ; U6 small nuclear RNA ; Positive Transcriptional Elongation Factor B (EC 2.7.11.-)
    Language English
    Publishing date 2009-04-06
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ISSN 1555-8584
    ISSN (online) 1555-8584
    DOI 10.4161/rna.6.2.8115
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: A Cyclin T1 point mutation that abolishes positive transcription elongation factor (P-TEFb) binding to Hexim1 and HIV tat.

    Verstraete, Nina / Kuzmina, Alona / Diribarne, Gaelle / Nguyen, Van Trung / Kobbi, Lydia / Ludanyi, Monika / Taube, Ran / Bensaude, Olivier

    Retrovirology

    2014  Volume 11, Page(s) 50

    Abstract: Background: The positive transcription elongation factor b (P-TEFb) plays an essential role in activating HIV genome transcription. It is recruited to the HIV LTR promoter through an interaction between the Tat viral protein and its Cyclin T1 subunit. P- ...

    Abstract Background: The positive transcription elongation factor b (P-TEFb) plays an essential role in activating HIV genome transcription. It is recruited to the HIV LTR promoter through an interaction between the Tat viral protein and its Cyclin T1 subunit. P-TEFb activity is inhibited by direct binding of its subunit Cyclin T (1 or 2) with Hexim (1 or 2), a cellular protein, bound to the 7SK small nuclear RNA. Hexim1 competes with Tat for P-TEFb binding.
    Results: Mutations that impair human Cyclin T1/Hexim1 interaction were searched using systematic mutagenesis of these proteins coupled with a yeast two-hybrid screen for loss of protein interaction. Evolutionary conserved Hexim1 residues belonging to an unstructured peptide located N-terminal of the dimerization domain, were found to be critical for P-TEFb binding. Random mutagenesis of the N-terminal region of Cyclin T1 provided identification of single amino-acid mutations that impair Hexim1 binding in human cells. Furthermore, conservation of critical residues supported the existence of a functional Hexim1 homologue in nematodes.
    Conclusions: Single Cyclin T1 amino-acid mutations that impair Hexim1 binding are located on a groove between the two cyclin folds and define a surface overlapping the HIV-1 Tat protein binding surface. One residue, Y175, in the centre of this groove was identified as essential for both Hexim1 and Tat binding to P-TEFb as well as for HIV transcription.
    MeSH term(s) Cyclin T/chemistry ; Cyclin T/metabolism ; Humans ; Hydrogen Bonding ; Point Mutation ; Positive Transcriptional Elongation Factor B/metabolism ; Protein Folding ; RNA-Binding Proteins/metabolism ; Structure-Activity Relationship ; Transcription Factors ; Two-Hybrid System Techniques ; tat Gene Products, Human Immunodeficiency Virus/metabolism
    Chemical Substances CCNT1 protein, human ; Cyclin T ; HEXIM1 protein, human ; RNA-Binding Proteins ; Transcription Factors ; tat Gene Products, Human Immunodeficiency Virus ; Positive Transcriptional Elongation Factor B (EC 2.7.11.-)
    Language English
    Publishing date 2014-07-01
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ISSN 1742-4690
    ISSN (online) 1742-4690
    DOI 10.1186/1742-4690-11-50
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Ubiquitination of HEXIM1 by HDM2.

    Lau, Joanne / Lew, Qiao Jing / Diribarne, Gaelle / Michels, Annemieke A / Dey, Anwesha / Bensaude, Olivier / Lane, David P / Chao, Sheng-Hao

    Cell cycle (Georgetown, Tex.)

    2009  Volume 8, Issue 14, Page(s) 2247–2254

    Abstract: Hexamethylene bis-acetamide inducible protein 1 (HEXIM1) is an inhibitor of the positive transcription elongation factor b (P-TEFb), which controls RNA polymerase II transcription and human immunodeficiency virus Tat transactivation. In cells, more than ... ...

    Abstract Hexamethylene bis-acetamide inducible protein 1 (HEXIM1) is an inhibitor of the positive transcription elongation factor b (P-TEFb), which controls RNA polymerase II transcription and human immunodeficiency virus Tat transactivation. In cells, more than half of P-TEFb is associated with HEXIM1 resulting in the inactivation of P-TEFb. Recently, we found that nucleophosmin (NPM), a key factor involved in p53 signaling pathway, interacts with HEXIM1 and activates P-TEFb-dependent transcription. Here we report that human double minute-2 protein (HDM2), a p53-specific E3 ubiquitin ligase, specifically ubiquitinates HEXIM1 through the lysine residues located within the basic region of HEXIM1. However, the HDM2-induced HEXIM1 ubiquitination does not lead to proteasome-mediated protein degradation. Fusion of ubiquitin to HEXIM1 demonstrates stronger inhibition on P-TEFb-dependent transcription. Our results demonstrate that HDM2 functions as a specific E3 ubiquitin ligase for HEXIM1, suggesting a possible role for HEXIM1 ubiquitination in the regulation of P-TEFb activity.
    MeSH term(s) Cell Line ; Cysteine Proteinase Inhibitors/pharmacology ; Humans ; Leupeptins/pharmacology ; Nuclear Proteins/metabolism ; Positive Transcriptional Elongation Factor B/genetics ; Positive Transcriptional Elongation Factor B/metabolism ; Proto-Oncogene Proteins c-mdm2/metabolism ; RNA-Binding Proteins/metabolism ; Signal Transduction ; Tumor Suppressor Protein p53/metabolism ; Ubiquitin-Protein Ligases/metabolism ; Ubiquitination
    Chemical Substances Cysteine Proteinase Inhibitors ; HEXIM1 protein, human ; Leupeptins ; Nuclear Proteins ; RNA-Binding Proteins ; Tumor Suppressor Protein p53 ; nucleophosmin (117896-08-9) ; MDM2 protein, human (EC 2.3.2.27) ; Proto-Oncogene Proteins c-mdm2 (EC 2.3.2.27) ; Ubiquitin-Protein Ligases (EC 2.3.2.27) ; Positive Transcriptional Elongation Factor B (EC 2.7.11.-) ; benzyloxycarbonylleucyl-leucyl-leucine aldehyde (RF1P63GW3K)
    Language English
    Publishing date 2009-08-05
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2146183-1
    ISSN 1551-4005 ; 1538-4101 ; 1554-8627
    ISSN (online) 1551-4005
    ISSN 1538-4101 ; 1554-8627
    DOI 10.4161/cc.8.14.9015
    Database MEDical Literature Analysis and Retrieval System OnLINE

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