Genes & development (Gene Dev)

Publications in this journal

• Article: Human ALKBH7 is required for alkylation and oxidation-induced programmed necrosis.

  Dragony Fu, Jennifer J Jordan, Leona D Samson
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  ABSTRACT: Programmed necrosis has emerged as a crucial modulator of cell death in response to several forms of cellular stress. In one form of programmed necrotic cell death, induced by cytotoxic alkylating agents, hyperactivation of poly-ADP-ribose polymerase (PARP) leads to cellular NAD and ATP depletion, mitochondrial dysfunction, reactive oxygen species formation, and ensuing cell death. Here, we show that the protein encoded by the human AlkB homolog 7 (ALKBH7) gene plays a pivotal role in DNA-damaging agent-induced programmed necrosis by triggering the collapse of mitochondrial membrane potential and large-scale loss of mitochondrial function that lead to energy depletion and cellular demise. Depletion of ALKBH7 suppresses necrotic cell death induced by numerous alkylating and oxidizing agents while having no effect on apoptotic cell death. Like wild-type cells, ALKBH7-depleted cells undergo PARP hyperactivation and NAD depletion after severe DNA damage but, unlike wild-type cells, exhibit rapid recovery of intracellular NAD and ATP levels. Consistent with the recovery of cellular bioenergetics, ALKBH7-depleted cells maintain their mitochondrial membrane potential, plasma membrane integrity, and viability. Our results uncover a novel role for a mammalian AlkB homolog in programmed necrosis, presenting a new target for therapeutic intervention in cancer cells that are resistant to apoptotic cell death.
  Genes & development 05/2013;
• Article: Dual function of the McaS small RNA in controlling biofilm formation.

  Mikkel Girke Jørgensen, Maureen K Thomason, Johannes Havelund, Poul Valentin-Hansen, Gisela Storz
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  ABSTRACT: Many bacterial small RNAs (sRNAs) regulate gene expression through base-pairing with mRNAs, and it has been assumed that these sRNAs act solely by this one mechanism. Here we report that the multicellular adhesive (McaS) sRNA of Escherichia coli uniquely acts by two different mechanisms: base-pairing and protein titration. Previous work established that McaS base pairs with the mRNAs encoding master transcription regulators of curli and flagella synthesis, respectively, resulting in down-regulation and up-regulation of these important cell surface structures. In this study, we demonstrate that McaS activates synthesis of the exopolysaccharide β-1,6 N-acetyl-D-glucosamine (PGA) by binding the global RNA-binding protein CsrA, a negative regulator of pgaA translation. The McaS RNA bears at least two CsrA-binding sequences, and inactivation of these sites compromises CsrA binding, PGA regulation, and biofilm formation. Moreover, ectopic McaS expression leads to induction of two additional CsrA-repressed genes encoding diguanylate cyclases. Collectively, our study shows that McaS is a dual-function sRNA with roles in the two major post-transcriptional regulons controlled by the RNA-binding proteins Hfq and CsrA.
  Genes & development 05/2013;
• Article: Molecular antagonism between X-chromosome and autosome signals determines nematode sex.

  Behnom Farboud, Paola Nix, Margaret M Jow, John M Gladden, Barbara J Meyer
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  ABSTRACT: Sex is determined in Caenorhabditis elegans by the ratio of X chromosomes to the sets of autosomes, the X:A signal. A set of genes called X signal elements (XSEs) communicates X-chromosome dose by repressing the masculinizing sex determination switch gene xol-1 (XO lethal) in a dose-dependent manner. xol-1 is active in 1X:2A embryos (males) but repressed in 2X:2A embryos (hermaphrodites). Here we showed that the autosome dose is communicated by a set of autosomal signal elements (ASEs) that act in a cumulative, dose-dependent manner to counter XSEs by stimulating xol-1 transcription. We identified new ASEs and explored the biochemical basis by which ASEs antagonize XSEs to determine sex. Multiple antagonistic molecular interactions carried out on a single promoter explain how different X:A values elicit different sexual fates. XSEs (nuclear receptors and homeodomain proteins) and ASEs (T-box and zinc finger proteins) bind directly to several sites on xol-1 to counteract each other's activities and thereby regulate xol-1 transcription. Disrupting ASE- and XSE-binding sites in vivo recapitulated the misregulation of xol-1 transcription caused by disrupting cognate signal element genes. XSE- and ASE-binding sites are distinct and nonoverlapping, suggesting that direct competition for xol-1 binding is not how XSEs counter ASEs. Instead, XSEs likely antagonize ASEs by recruiting cofactors with reciprocal activities that induce opposite transcriptional states. Most ASE- and XSE-binding sites overlap xol-1's -1 nucleosome, which carries activating chromatin marks only when xol-1 is turned on. Coactivators and corepressors tethered by proteins similar to ASEs and XSEs are known to deposit and remove such marks. The concept of a sex signal comprising competing XSEs and ASEs arose as a theory for fruit flies a century ago. Ironically, while the recent work of others showed that the fly sex signal does not fit this simple paradigm, our work shows that the worm signal does.
  Genes & development 05/2013;
• Article: Frequent provirus insertional mutagenesis of Notch1 in thymomas of MMTVD/myc transgenic mice suggests a collaboration of c-myc and Notch1 for oncogenesis

  L Girard, Z Hanna, N Beaulieu, CD Hoemann, C Simard, CA Kozak, P Jolicoeur
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  ABSTRACT: The MMTVD/myc transgenic mice spontaneously develop oligoclonal CD4+CD8+ T-cell tumors. We used provirus insertional mutagenesis in these mice to identify putative collaborators of c-myc. We found that Notch1 was mutated in a high proportion (52%) of these tumors. Proviruses were inserted upstream of the exon coding for the transmembrane domain and in both transcriptional orientations. These mutations led to high expression of truncated Notch1 RNAs and proteins (86-110 kD). In addition, many Notch1-rearranged tumors showed elevated levels of full-length Notch1 transcripts, whereas nearly all showed increased levels of full-length (330-kD) or close to full-length (280-kD) Notch1 proteins. The 5' end of the truncated RNAs were determined for some tumors by use of RT-PCR and 5' RACE techniques. Depending on the orientation of the proviruses, viral LTR or cryptic promoters appeared to be utilized, and coding potential began in most cases in the transmembrane domain. Pulse-chase experiments revealed that the 330-kD Notch1 proteins were processed into 110- and 280-kD cleavage products. These results suggest that Notch1 can be a frequent collaborator of c-myc for oncogenesis. Furthermore, our data indicate that Notch1 alleles mutated by provirus insertion can lead to increased expression of truncated and full-length (330/280-kD) Notch1 proteins, both being produced in a cleaved and uncleaved form.
  Genes & development 05/2013; 10(15):1930-44.
• Article: The DEAH-box helicase DHX36 mediates dendritic localization of the neuronal precursor-microRNA-134.

  Silvia Bicker, Sharof Khudayberdiev, Kerstin Weiß, Kathleen Zocher, Stefan Baumeister, Gerhard Schratt
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  ABSTRACT: Specific microRNAs (miRNAs), including miR-134, localize to neuronal dendrites, where they control synaptic protein synthesis and plasticity. However, the mechanism of miRNA transport is unknown. We found that the neuronal precursor-miRNA-134 (pre-miR-134) accumulates in dendrites of hippocampal neurons and at synapses in vivo. Dendritic localization of pre-miR-134 is mediated by the DEAH-box helicase DHX36, which directly associates with the pre-miR-134 terminal loop. DHX36 function is required for miR-134-dependent inhibition of target gene expression and the control of dendritic spine size. Dendritically localized pre-miR-134 could provide a local source of miR-134 that can be mobilized in an activity-dependent manner during plasticity.
  Genes & development 05/2013; 27(9):991-6.
• Article: Global genomic profiling reveals an extensive p53-regulated autophagy program contributing to key p53 responses.

  Daniela Kenzelmann Broz, Stephano Spano Mello, Kathryn T Bieging, Dadi Jiang, Rachel L Dusek, Colleen A Brady, Arend Sidow, Laura D Attardi
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  ABSTRACT: The mechanisms by which the p53 tumor suppressor acts remain incompletely understood. To gain new insights into p53 biology, we used high-throughput sequencing to analyze global p53 transcriptional networks in primary mouse embryo fibroblasts in response to DNA damage. Chromatin immunoprecipitation sequencing reveals 4785 p53-bound sites in the genome located near 3193 genes involved in diverse biological processes. RNA sequencing analysis shows that only a subset of p53-bound genes is transcriptionally regulated, yielding a list of 432 p53-bound and regulated genes. Interestingly, we identify a host of autophagy genes as direct p53 target genes. While the autophagy program is regulated predominantly by p53, the p53 family members p63 and p73 contribute to activation of this autophagy gene network. Induction of autophagy genes in response to p53 activation is associated with enhanced autophagy in diverse settings and depends on p53 transcriptional activity. While p53-induced autophagy does not affect cell cycle arrest in response to DNA damage, it is important for both robust p53-dependent apoptosis triggered by DNA damage and transformation suppression by p53. Together, our data highlight an intimate connection between p53 and autophagy through a vast transcriptional network and indicate that autophagy contributes to p53-dependent apoptosis and cancer suppression.
  Genes & development 05/2013; 27(9):1016-31.
• Article: Genome-wide RNAi screens in human brain tumor isolates reveal a novel viability requirement for PHF5A.

  Christopher G Hubert, Robert K Bradley, Yu Ding, Chad M Toledo, Jacob Herman, Kyobi Skutt-Kakaria, Emily J Girard, Jerry Davison, Jason Berndt, Philip Corrin, Justin Hardcastle, Ryan Basom, Jeffery J Delrow, Thomas Webb, Steven M Pollard, Jeongwu Lee, James M Olson, Patrick J Paddison
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  ABSTRACT: To identify key regulators of human brain tumor maintenance and initiation, we performed multiple genome-wide RNAi screens in patient-derived glioblastoma multiforme (GBM) stem cells (GSCs). These screens identified the plant homeodomain (PHD)-finger domain protein PHF5A as differentially required for GSC expansion, as compared with untransformed neural stem cells (NSCs) and fibroblasts. Given PHF5A's known involvement in facilitating interactions between the U2 snRNP complex and ATP-dependent helicases, we examined cancer-specific roles in RNA splicing. We found that in GSCs, but not untransformed controls, PHF5A facilitates recognition of exons with unusual C-rich 3' splice sites in thousands of essential genes. PHF5A knockdown in GSCs, but not untransformed NSCs, astrocytes, or fibroblasts, inhibited splicing of these genes, leading to cell cycle arrest and loss of viability. Notably, pharmacologic inhibition of U2 snRNP activity phenocopied PHF5A knockdown in GSCs and also in NSCs or fibroblasts overexpressing MYC. Furthermore, PHF5A inhibition compromised GSC tumor formation in vivo and inhibited growth of established GBM patient-derived xenograft tumors. Our results demonstrate a novel viability requirement for PHF5A to maintain proper exon recognition in brain tumor-initiating cells and may provide new inroads for novel anti-GBM therapeutic strategies.
  Genes & development 05/2013; 27(9):1032-45.
• Article: The family that eats together stays together: new p53 family transcriptional targets in autophagy.

  Marco Napoli, Elsa R Flores
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  ABSTRACT: Autophagy is a biological process that is crucial to maintain cellular homeostasis and is regulated by several metabolic pathways, including the p53 tumor suppressor pathway. In this issue of Genes & Development, Kenzelmann Broz and colleagues (pp. 1016-1031) show how the p53 family as a whole, including p63 and p73, collaborate in controlling autophagy to support tumor suppression.
  Genes & development 05/2013; 27(9):971-4.
• Article: Dynamic binding of RBPJ is determined by Notch signaling status.

  David Castel, Philippos Mourikis, Stefanie J J Bartels, Arie B Brinkman, Shahragim Tajbakhsh, Hendrik G Stunnenberg
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  ABSTRACT: Notch signaling plays crucial roles in mediating cell fate choices in all metazoans largely by specifying the transcriptional output of one cell in response to a neighboring cell. The DNA-binding protein RBPJ is the principle effector of this pathway in mammals and, together with the transcription factor moiety of Notch (NICD), regulates the expression of target genes. The prevalent view presumes that RBPJ statically occupies consensus binding sites while exchanging repressors for activators in response to NICD. We present the first specific RBPJ chromatin immunoprecipitation and high-throughput sequencing study in mammalian cells. To dissect the mode of transcriptional regulation by RBPJ and identify its direct targets, whole-genome binding profiles were generated for RBPJ; its coactivator, p300; NICD; and the histone H3 modifications H3 Lys 4 trimethylation (H3K4me3), H3 Lys 4 monomethylation (H3K4me1), and histone H3 Lys 27 acetylation (H3K27ac) in myogenic cells under active or inhibitory Notch signaling conditions. Our results demonstrate dynamic binding of RBPJ in response to Notch activation at essentially all sites co-occupied by NICD. Additionally, we identify a distinct set of sites where RBPJ recruits neither NICD nor p300 and binds DNA statically, irrespective of Notch activity. These findings significantly modify our views on how RBPJ and Notch signaling mediate their activities and consequently impact on cell fate decisions.
  Genes & development 05/2013; 27(9):1059-71.
• Article: The T-box transcription factor Eomesodermin is essential for AVE induction in the mouse embryo.

  Sonja Nowotschin, Ita Costello, Anna Piliszek, Gloria S Kwon, Chai-An Mao, William H Klein, Elizabeth J Robertson, Anna-Katerina Hadjantonakis
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  ABSTRACT: Reciprocal inductive interactions between the embryonic and extraembryonic tissues establish the anterior-posterior (AP) axis of the early mouse embryo. The anterior visceral endoderm (AVE) signaling center emerges at the distal tip of the embryo at embryonic day 5.5 and translocates to the prospective anterior side of the embryo. The process of AVE induction and migration are poorly understood. Here we demonstrate that the T-box gene Eomesodermin (Eomes) plays an essential role in AVE recruitment, in part by directly activating the homeobox transcription factor Lhx1. Thus, Eomes function in the visceral endoderm (VE) initiates an instructive transcriptional program controlling AP identity.
  Genes & development 05/2013; 27(9):997-1002.
• Article: Protein segregase meddles in remodeling of mRNA-protein complexes.

  Chyi-Ying A Chen, Ann-Bin Shyu
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  ABSTRACT: Remodeling of RNA-protein complexes (mRNPs) plays a critical role in mRNA biogenesis and metabolism. However, relatively little is known about the underlying mechanism and regulation of the mRNP remodeling. In this issue of Genes & Development, Zhou and colleagues (pp. 1046-1058) report that a protein remodeling machine, the p97-UBXD8 complex, disassembles mRNPs containing the AU-rich elements (AREs) bound by HuR proteins in a nondegradative, ubiquitin signaling-dependent manner, revealing a novel mechanism to regulate mRNA turnover.
  Genes & development 05/2013; 27(9):980-4.
• Article: The retinoblastoma protein induces apoptosis directly at the mitochondria.

  Keren I Hilgendorf, Elizaveta S Leshchiner, Simona Nedelcu, Mindy A Maynard, Eliezer Calo, Alessandra Ianari, Loren D Walensky, Jacqueline A Lees
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  ABSTRACT: The retinoblastoma protein gene RB-1 is mutated in one-third of human tumors. Its protein product, pRB (retinoblastoma protein), functions as a transcriptional coregulator in many fundamental cellular processes. Here, we report a nonnuclear role for pRB in apoptosis induction via pRB's direct participation in mitochondrial apoptosis. We uncovered this activity by finding that pRB potentiated TNFα-induced apoptosis even when translation was blocked. This proapoptotic function was highly BAX-dependent, suggesting a role in mitochondrial apoptosis, and accordingly, a fraction of endogenous pRB constitutively associated with mitochondria. Remarkably, we found that recombinant pRB was sufficient to trigger the BAX-dependent permeabilization of mitochondria or liposomes in vitro. Moreover, pRB interacted with BAX in vivo and could directly bind and conformationally activate BAX in vitro. Finally, by targeting pRB specifically to mitochondria, we generated a mutant that lacked pRB's classic nuclear roles. This mito-tagged pRB retained the ability to promote apoptosis in response to TNFα and also additional apoptotic stimuli. Most importantly, induced expression of mito-tagged pRB in Rb(-/-);p53(-/-) tumors was sufficient to block further tumor development. Together, these data establish a nontranscriptional role for pRB in direct activation of BAX and mitochondrial apoptosis in response to diverse stimuli, which is profoundly tumor-suppressive.
  Genes & development 04/2013;
• Article: The p97-UBXD8 complex destabilizes mRNA by promoting release of ubiquitinated HuR from mRNP.

  Hua-Lin Zhou, Cuiyu Geng, Guangbin Luo, Hua Lou
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  ABSTRACT: The assembly and disassembly of ribonucleoproteins (RNPs) are dynamic processes that control every step of RNA metabolism, including mRNA stability. However, our knowledge of how RNP remodeling is achieved is largely limited to RNA helicase functions. Here, we report a previously unknown mechanism that implicates the ATPase p97, a protein-remodeling machine, in the dynamic regulation of mRNP disassembly. We found that p97 and its cofactor, UBXD8, destabilize p21, MKP-1, and SIRT1, three established mRNA targets of the RNA-binding protein HuR, by promoting release of HuR from mRNA. Importantly, ubiquitination of HuR with a short K29 chain serves as the signal for release. When cells are subjected to stress conditions, the steady-state levels of HuR ubiquitination change, suggesting a new mechanism through which HuR mediates the stress response. Our studies reveal a new paradigm in RNA biology: nondegradative ubiquitin signaling-dependent disassembly of mRNP promoted by the p97-UBXD8 complex to control mRNA stability.
  Genes & development 04/2013;
• Article: A RANKL-PKCβ-TFEB signaling cascade is necessary for lysosomal biogenesis in osteoclasts.

  Mathieu Ferron, Carmine Settembre, Junko Shimazu, Julie Lacombe, Shigeaki Kato, David J Rawlings, Andrea Ballabio, Gerard Karsenty
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  ABSTRACT: Bone resorption by osteoclasts requires a large number of lysosomes that release proteases in the resorption lacuna. Whether lysosomal biogenesis is a consequence of the action of transcriptional regulators of osteoclast differentiation or is under the control of a different and specific transcriptional pathway remains unknown. We show here, through cell-based assays and cell-specific gene deletion experiments in mice, that the osteoclast differentiation factor RANKL promotes lysosomal biogenesis once osteoclasts are differentiated through the selective activation of TFEB, a member of the MITF/TFE family of transcription factors. This occurs following PKCβ phosphorylation of TFEB on three serine residues located in its last 15 amino acids. This post-translational modification stabilizes and increases the activity of this transcription factor. Supporting these biochemical observations, mice lacking in osteoclasts-either TFEB or PKCβ-show decreased lysosomal gene expression and increased bone mass. Altogether, these results uncover a RANKL-dependent signaling pathway taking place in differentiated osteoclasts and culminating in the activation of TFEB to enhance lysosomal biogenesis-a necessary step for proper bone resorption.
  Genes & development 04/2013;
• Article: Numerical constraints and feedback control of double-strand breaks in mouse meiosis.

  Liisa Kauppi, Marco Barchi, Julian Lange, Frédéric Baudat, Maria Jasin, Scott Keeney
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  ABSTRACT: Different organisms display widely different numbers of the programmed double-strand breaks (DSBs) that initiate meiotic recombination (e.g., hundreds per meiocyte in mice and humans vs. dozens in nematodes), but little is known about what drives these species-specific DSB set points or the regulatory pathways that control them. Here we examine male mice with a lowered dosage of SPO11, the meiotic DSB catalyst, to gain insight into the effect of reduced DSB numbers on mammalian chromosome dynamics. An approximately twofold DSB reduction was associated with the reduced ability of homologs to synapse along their lengths, provoking prophase arrest and, ultimately, sterility. In many spermatocytes, chromosome subsets displayed a mix of synaptic failure and synapsis with both homologous and nonhomologous partners ("chromosome tangles"). The X chromosome was nearly always involved in tangles, and small autosomes were involved more often than large ones. We conclude that homolog pairing requirements dictate DSB set points during meiosis. Importantly, our results reveal that karyotype is a key factor: Smaller autosomes and heteromorphic sex chromosomes become weak links when DSBs are reduced below a critical threshold. Unexpectedly, unsynapsed chromosome segments trapped in tangles displayed an elevated density of DSB markers later in meiotic prophase. The unsynapsed portion of the X chromosome in wild-type males also showed evidence that DSB numbers increased as prophase progressed. These findings point to the existence of a feedback mechanism that links DSB number and distribution with interhomolog interactions.
  Genes & development 04/2013;
• Article: Tumor suppressor activity of the ERK/MAPK pathway by promoting selective protein degradation.

  Xavier Deschênes-Simard, Marie-France Gaumont-Leclerc, Véronique Bourdeau, Frédéric Lessard, Olga Moiseeva, Valérie Forest, Sebastian Igelmann, Frédérick A Mallette, Marc K Saba-El-Leil, Sylvain Meloche, Fred Saad, Anne-Marie Mes-Masson, Gerardo Ferbeyre
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  ABSTRACT: Constitutive activation of growth factor signaling pathways paradoxically triggers a cell cycle arrest known as cellular senescence. In primary cells expressing oncogenic ras, this mechanism effectively prevents cell transformation. Surprisingly, attenuation of ERK/MAP kinase signaling by genetic inactivation of Erk2, RNAi-mediated knockdown of ERK1 or ERK2, or MEK inhibitors prevented the activation of the senescence mechanism, allowing oncogenic ras to transform primary cells. Mechanistically, ERK-mediated senescence involved the proteasome-dependent degradation of proteins required for cell cycle progression, mitochondrial functions, cell migration, RNA metabolism, and cell signaling. This senescence-associated protein degradation (SAPD) was observed not only in cells expressing ectopic ras, but also in cells that senesced due to short telomeres. Individual RNAi-mediated inactivation of SAPD targets was sufficient to restore senescence in cells transformed by oncogenic ras or trigger senescence in normal cells. Conversely, the anti-senescence viral oncoproteins E1A, E6, and E7 prevented SAPD. In human prostate neoplasms, high levels of phosphorylated ERK were found in benign lesions, correlating with other senescence markers and low levels of STAT3, one of the SAPD targets. We thus identified a mechanism that links aberrant activation of growth signaling pathways and short telomeres to protein degradation and cellular senescence.
  Genes & development 04/2013;
• Article: Respiration control of multicellularity in Bacillus subtilis by a complex of the cytochrome chain with a membrane-embedded histidine kinase.

  Ilana Kolodkin-Gal, Alexander K W Elsholz, Christine Muth, Peter R Girguis, Roberto Kolter, Richard Losick
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  ABSTRACT: Bacillus subtilis forms organized multicellular communities known as biofilms wherein the individual cells are held together by a self-produced extracellular matrix. The environmental signals that promote matrix synthesis remain largely unknown. We discovered that one such signal is impaired respiration. Specifically, high oxygen levels suppressed synthesis of the extracellular matrix. In contrast, low oxygen levels, in the absence of an alternative electron acceptor, led to increased matrix production. The response to impaired respiration was blocked in a mutant lacking cytochromes caa3 and bc and markedly reduced in a mutant lacking kinase KinB. Mass spectrometry of proteins associated with KinB showed that the kinase was in a complex with multiple components of the aerobic respiratory chain. We propose that KinB is activated via a redox switch involving interaction of its second transmembrane segment with one or more cytochromes under conditions of reduced electron transport. In addition, a second kinase (KinA) contributes to the response to impaired respiration. Evidence suggests that KinA is activated by a decrease in the nicotinamide adenine dinucleotide (NAD(+))/NADH ratio via binding of NAD(+) to the kinase in a PAS domain A-dependent manner. Thus, B. subtilis switches from a unicellular to a multicellular state by two pathways that independently respond to conditions of impaired respiration.
  Genes & development 04/2013;
• Article: Suv4-20h2 mediates chromatin compaction and is important for cohesin recruitment to heterochromatin.

  Matthias Hahn, Silvia Dambacher, Stanimir Dulev, Anastasia Yurievna Kuznetsova, Simon Eck, Stefan Wörz, Dennis Sadic, Maike Schulte, Jan-Philipp Mallm, Andreas Maiser, Pierre Debs, Harald von Melchner, Heinrich Leonhardt, Lothar Schermelleh, Karl Rohr, Karsten Rippe, Zuzana Storchova, Gunnar Schotta
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  ABSTRACT: Cohesin plays an important role in chromatid cohesion and has additional functions in higher-order chromatin organization and in transcriptional regulation. The binding of cohesin to euchromatic regions is largely mediated by CTCF or the mediator complex. However, it is currently unknown how cohesin is recruited to pericentric heterochromatin in mammalian cells. Here we define the histone methyltransferase Suv4-20h2 as a major structural constituent of heterochromatin that mediates chromatin compaction and cohesin recruitment. Suv4-20h2 stably associates with pericentric heterochromatin through synergistic interactions with multiple heterochromatin protein 1 (HP1) molecules, resulting in compaction of heterochromatic regions. Suv4-20h mutant cells display an overall reduced chromatin compaction and an altered chromocenter organization in interphase referred to as "chromocenter scattering." We found that Suv4-20h-deficient cells display chromosome segregation defects during mitosis that coincide with reduced sister chromatid cohesion. Notably, cohesin subunits interact with Suv4-20h2 both in vitro and in vivo. This interaction is necessary for cohesin binding to heterochromatin, as Suv4-20h mutant cells display substantially reduced cohesin levels at pericentric heterochromatin. This defect is most prominent in G0-phase cells, where cohesin is virtually lost from heterochromatin, suggesting that Suv4-20h2 is involved in the initial loading or maintenance of cohesion subunits. In summary, our data provide the first compelling evidence that Suv4-20h2 plays essential roles in regulating nuclear architecture and ensuring proper chromosome segregation.
  Genes & development 04/2013;