Centre for Cancer Research - Research Publications

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    Tight regulation of ubiquitin-mediated DNA damage response by USP3 preserves the functional integrity of hematopoietic stem cells
    Lancini, C ; van den Berk, PCM ; Vissers, JHA ; Gargiulo, G ; Song, J-Y ; Hulsman, D ; Serresi, M ; Tanger, E ; Blom, M ; Vens, C ; van Lohuizen, M ; Jacobs, H ; Citterio, E (ROCKEFELLER UNIV PRESS, 2014-08-25)
    Histone ubiquitination at DNA breaks is required for activation of the DNA damage response (DDR) and DNA repair. How the dynamic removal of this modification by deubiquitinating enzymes (DUBs) impacts genome maintenance in vivo is largely unknown. To address this question, we generated mice deficient for Ub-specific protease 3 (USP3; Usp3Δ/Δ), a histone H2A DUB which negatively regulates ubiquitin-dependent DDR signaling. Notably, USP3 deletion increased the levels of histone ubiquitination in adult tissues, reduced the hematopoietic stem cell (HSC) reserves over time, and shortened animal life span. Mechanistically, our data show that USP3 is important in HSC homeostasis, preserving HSC self-renewal, and repopulation potential in vivo and proliferation in vitro. A defective DDR and unresolved spontaneous DNA damage contribute to cell cycle restriction of Usp3Δ/Δ HSCs. Beyond the hematopoietic system, Usp3Δ/Δ animals spontaneously developed tumors, and primary Usp3Δ/Δ cells failed to preserve chromosomal integrity. These findings broadly support the regulation of chromatin ubiquitination as a key pathway in preserving tissue function through modulation of the response to genotoxic stress.
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    Inter-subunit interactions that coordinate Rad51s activities
    Grigorescu, AA ; Vissers, JHA ; Ristic, D ; Pigli, YZ ; Lynch, TW ; Wyman, C ; Rice, PA (OXFORD UNIV PRESS, 2009-02)
    Rad51 is the central catalyst of homologous recombination in eukaryotes and is thus critical for maintaining genomic integrity. Recent crystal structures of filaments formed by Rad51 and the closely related archeal RadA and eubacterial RecA proteins place the ATPase site at the protomeric interface. To test the relevance of this feature, we mutated conserved residues at this interface and examined their effects on key activities of Rad51: ssDNA-stimulated ATP hydrolysis, DNA binding, polymerization on DNA substrates and catalysis of strand-exchange reactions. Our results show that the interface seen in the crystal structures is very important for nucleoprotein filament formation. H352 and R357 of yeast Rad51 are essential for assembling the catalytically competent form of the enzyme on DNA substrates and coordinating its activities. However, contrary to some previous suggestions, neither of these residues is critical for ATP hydrolysis.
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    A genome-wide RNAi screen in mouse embryonic stem cells identifies Mp1 as a key mediator of differentiation
    Westerman, BA ; Braat, AK ; Taub, N ; Potman, M ; Vissers, JHA ; Blom, M ; Verhoeven, E ; Stoop, H ; Gillis, A ; Velds, A ; Nijkamp, W ; Beijersbergen, R ; Huber, LA ; Looijenga, LHJ ; van Lohuizen, M (ROCKEFELLER UNIV PRESS, 2011-12-19)
    Despite intense investigation of intrinsic and extrinsic factors that regulate pluripotency, the process of initial fate commitment of embryonic stem (ES) cells is still poorly understood. We used a genome-wide short hairpin RNA screen in mouse ES cells to identify genes that are essential for initiation of differentiation. Knockdown of the scaffolding protein Mek binding protein 1 (Mp1, also known as Lamtor3 or Map2k1ip1) stimulated self-renewal of ES cells, blocked differentiation, and promoted proliferation. Fibroblast growth factor 4 (FGF4) signaling is required for initial fate commitment of ES cells. Knockdown of Mp1 inhibited FGF4-induced differentiation but did not alter FGF4-driven proliferation. This uncoupling of differentiation and proliferation was also observed when oncogenic Ras isoforms were overexpressed in ES cells. Knockdown of Mp1 redirected FGF4 signaling from differentiation toward pluripotency and up-regulated the pluripotency-related genes Esrrb, Rex1, Tcl1, and Sox2. We also found that human germ cell tumors (GCTs) express low amounts of Mp1 in the invasive embryonic carcinoma and seminoma histologies and higher amounts of Mp1 in the noninvasive carcinoma in situ precursor and differentiated components. Knockdown of Mp1 in invasive GCT cells resulted in resistance to differentiation, thereby showing a functional role for Mp1 both in normal differentiation of ES cells and in germ cell cancer.
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    The many faces of ubiquitinated histone H2A: insights from the DUBs
    Vissers, JHA ; Nicassio, F ; van Lohuizen, M ; Di Fiore, PP ; Citterio, E (BMC, 2008)
    Monoubiquitination of H2A is a major histone modification in mammalian cells. Understanding how monoubiquitinated H2A (uH2A) regulates DNA-based processes in the context of chromatin is a challenging question. Work in the past years linked uH2A to transcriptional repression by the Polycomb group proteins of developmental regulators. Recently, a number of mammalian deubiquitinating enzymes (DUBs) that catalyze the removal of ubiquitin from H2A have been discovered. These studies provide convincing evidence that H2A deubiquitination is connected with gene activation. In addition, uH2A regulatory enzymes have crucial roles in the cellular response to DNA damage and in cell cycle progression. In this review we will discuss new insights into uH2A biology, with emphasis on the H2A DUBs.
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    The Scalloped and Nerfin-1 Transcription Factors Cooperate to Maintain Neuronal Cell Fate
    Vissers, JHA ; Froldi, F ; Schroder, J ; Papenfuss, AT ; Cheng, LY ; Harvey, KF (CELL PRESS, 2018-11-06)
    The ability of cells to stably maintain their fate is governed by specific transcription regulators. Here, we show that the Scalloped (Sd) and Nervous fingers-1 (Nerfin-1) transcription factors physically and functionally interact to maintain medulla neuron fate in the Drosophila melanogaster CNS. Using Targeted DamID, we find that Sd and Nerfin-1 occupy a highly overlapping set of target genes, including regulators of neural stem cell and neuron fate, and signaling pathways that regulate CNS development such as Notch and Hippo. Modulation of either Sd or Nerfin-1 activity causes medulla neurons to dedifferentiate to a stem cell-like state, and this is mediated at least in part by Notch pathway deregulation. Intriguingly, orthologs of Sd and Nerfin-1 have also been implicated in control of neuronal cell fate decisions in both worms and mammals. Our data indicate that this transcription factor pair exhibits remarkable biochemical and functional conservation across metazoans.