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64 Publications

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    Tjian Lab
    06/21/02 | Neurodegeneration. A glutamine-rich trail leads to transcription factors.
    Freiman RN, Tjian R
    Science . 2002 Jun 21;296(5576):2149-50. doi: 10.1073/pnas.1100640108
    Tjian Lab
    06/01/02 | Human CRSP interacts with RNA polymerase II CTD and adopts a specific CTD-bound conformation.
    Näär AM, Taatjes DJ, Zhai W, Nogales E, Tjian R
    Genes & Development. 2002 Jun 1;16(11):1339-44. doi: 10.1073/pnas.1100640108

    Activation of gene transcription in mammalian cells requires several classes of coactivators that participate in different steps of the activation cascade. Using conventional and affinity chromatography, we have isolated a human coactivator complex that interacts directly with the C-terminal domain (CTD) of RNA polymerase II (Pol II). The CTD-binding complex is structurally and functionally indistinguishable from our previously isolated CRSP coactivator complex. The closely related, but transcriptionally inactive, ARC-L complex failed to interact with the CTD, indicating a significant biochemical difference between CRSP and ARC-L that may, in part, explain their functional divergence. Electron microscopy and three-dimensional single-particle reconstruction reveals a conformation for CTD-CRSP that is structurally distinct from unliganded CRSP or CRSP bound to SREBP-1a, but highly similar to CRSP bound to the VP16 activator. Together, our findings suggest that the human CRSP coactivator functions, at least in part, by mediating activator-dependent recruitment of RNA Pol II via the CTD.

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    Tjian Lab
    02/08/02 | Structure, function, and activator-induced conformations of the CRSP coactivator.
    Taatjes DJ, Näär AM, Andel F, Nogales E, Tjian R
    Science. 2002 Feb 8;295(5557):1058-62. doi: 10.1073/pnas.1100640108

    The human cofactor complexes ARC (activator-recruited cofactor) and CRSP (cofactor required for Sp1 activation) mediate activator-dependent transcription in vitro. Although these complexes share several common subunits, their structural and functional relationships remain unknown. Here, we report that affinity-purified ARC consists of two distinct multisubunit complexes: a larger complex, denoted ARC-L, and a smaller coactivator, CRSP. Reconstituted in vitro transcription with biochemically separated ARC-L and CRSP reveals differential cofactor functions. The ARC-L complex is transcriptionally inactive, whereas the CRSP complex is highly active. Structural determination by electron microscopy (EM) and three-dimensional reconstruction indicate substantial differences in size and shape between ARC-L and CRSP. Moreover, EM analysis of independently derived CRSP complexes reveals distinct conformations induced by different activators. These results suggest that CRSP may potentiate transcription via specific activator-induced conformational changes.

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    Tjian LabRubin Lab
    07/15/94 | The activities of two Ets-related transcription factors required for Drosophila eye development are modulated by the Ras/MAPK pathway.
    O’Neill EM, Rebay I, Tjian R, Rubin GM
    Cell. 1994 Jul 15;78(1):137-47. doi: 10.1186/gb-2007-8-7-r145

    We show that the activities of two Ets-related transcription factors required for normal eye development in Drosophila, pointed and yan, are regulated by the Ras1/MAPK pathway. The pointed gene codes for two related proteins, and we show that one form is a constitutive activator of transcription, while the activity of the other form is stimulated by the Ras1/MAPK pathway. Mutation of the single consensus MAPK phosphorylation site in the second form abrogates this responsiveness. yan is a negative regulator of photoreceptor determination, and genetic data suggest that it acts as an antagonist of Ras1. We demonstrate that yan can repress transcription and that this repression activity is negatively regulated by the Ras1/MAPK signal, most likely through direct phosphorylation of yan by MAPK.

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