28 research outputs found

    In vivo dissection of the chromosome condensation machinery: reversibility of condensation distinguishes contributions of condensin and cohesin

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    The machinery mediating chromosome condensation is poorly understood. To begin to dissect the in vivo function(s) of individual components, we monitored mitotic chromosome structure in mutants of condensin, cohesin, histone H3, and topoisomerase II (topo II). In budding yeast, both condensation establishment and maintenance require all of the condensin subunits, but not topo II activity or phospho-histone H3. Structural maintenance of chromosome (SMC) protein 2, as well as each of the three non-SMC proteins (Ycg1p, Ycs4p, and Brn1p), was required for chromatin binding of the condensin complex in vivo. Using reversible condensin alleles, we show that chromosome condensation does not involve an irreversible modification of condensin or chromosomes. Finally, we provide the first evidence of a mechanistic link between condensin and cohesin function. A model discussing the functional interplay between cohesin and condensin is presented

    Dopamine and Glutamate Induce Distinct Striatal Splice Forms of Ania-6, an RNA Polymerase II-Associated Cyclin

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    AbstractControl of neuronal gene expression by drugs or neurotransmitters is a critical step in long-term neural plasticity. Here, we show that a gene induced in the striatum by cocaine or direct dopamine stimulation, ania-6, is a member of a novel family of cyclins with homology to cyclins K/T/H/C. Further, different types of neurotransmitter stimulation cause selective induction of distinct ania-6 isoforms, through alternative splicing. The longer Ania-6 protein colocalizes with nuclear speckles and is associated with key elements of the RNA elongation/processing complex, including the hyperphosphorylated form of RNA polymerase II, the splicing factor SC-35, and the p110 PITSLRE cyclin-dependent kinase. Distinct types of neuronal stimulation may therefore differentially modulate nuclear RNA processing, through altered transcription and splicing of ania-6

    Monocyte Gene Expression Signature of Patients with Early Onset Coronary Artery Disease

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    The burden of cardiovascular disease (CVD) cannot be fully addressed by therapy targeting known pathophysiological pathways. Even with stringent control of all risk factors CVD events are only diminished by half. A number of additional pathways probably play a role in the development of CVD and might serve as novel therapeutic targets. Genome wide expression studies represent a powerful tool to identify such novel pathways. We compared the expression profiles in monocytes from twenty two young male patients with premature familial CAD with those from controls matched for age, sex and smoking status, without a family history of CVD. Since all patients were on statins and aspirin treatment, potentially affecting the expression of genes in monocytes, twelve controls were subsequently treated with simvastatin and aspirin for 6 and 2 weeks, respectively

    pRb and condensin—local control of global chromosome structure

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    Rb mutants exhibit aneuploidy and aberrant chromosome structure during mitosis. In this issue of Genes & Development, a new paper from Longworth and colleagues (1011–1024) describes both physical and functional interactions between Drosophila Rbf1 and the dCAP-D3 subunit of condensin II. This work directly implicates the Rb family proteins in mitotic chromosome condensation and suggests that a failure in targeting condensin II to chromatin underlies the aneuploidy in rbf1 mutants

    In vivo requirements for rDNA chromosome condensation reveal two cell-cycle-regulated pathways for mitotic chromosome folding

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    Chromosome condensation plays an essential role in the maintenance of genetic integrity. Using genetic, cell biological, and biochemical approaches, we distinguish two cell-cycle-regulated pathways for chromosome condensation in budding yeast. From G(2) to metaphase, we show that the condensation of the ∼1-Mb rDNA array is a multistep process, and describe condensin-dependent clustering, alignment, and resolution steps in chromosome folding. We functionally define a further postmetaphase chromosome assembly maturation step that is required for the maintenance of chromosome structural integrity during segregation. This late step in condensation requires the conserved mitotic kinase Ipl1/aurora in addition to condensin, but is independent of cohesin. Consistent with this, the late condensation pathway is initiated during the metaphase-to-anaphase transition, supports de novo condensation in cohesin mutants, and correlates with the Ipl1/aurora-dependent phosphorylation of condensin. These data provide insight into the molecular mechanisms of higher-order chromosome folding and suggest that two distinct condensation pathways, one involving cohesins and the other Ipl1/aurora, are required to modulate chromosome structure during mitosis

    EBP2 Plays a Key Role in Epstein-Barr Virus Mitotic Segregation and Is Regulated by Aurora Family Kinases

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    Epstein-Barr virus (EBV) genomes persist indefinitely in latently infected human cells, in part due to their ability to stably segregate during cell division. This process is mediated by the viral EBNA1 protein, which tethers the viral episomes to the cellular mitotic chromosomes. We have previously identified a mitotic chromosomal protein, human EBNA1 binding protein 2 (hEBP2), which binds to EBNA1 and enables EBNA1 to partition EBV-based plasmids in Saccharomyces cerevisiae. Using an RNA silencing approach, we show that hEBP2 is essential for the proliferation of human cells and that repression of hEBP2 severely decreases the ability of EBNA1 and EBV-based plasmids to bind mitotic chromosomes. When expressed in yeast, hEBP2 undergoes the same cell cycle-regulated association with the mitotic chromatin as in human cells, and using yeast temperature-sensitive mutant strains, we found that the attachment of hEBP2 to mitotic chromosomes was dependent on the Ipl1 kinase. Both RNA silencing of the Ipl1 orthologue in human cells (Aurora B) and specific inhibition of the Aurora B kinase activity with a small molecule confirmed a role for this kinase in enabling hEBP2 binding to human mitotic chromosomes, suggesting that this kinase can regulate EBV segregation

    The choice of distracting task can affect the quality of auditory evoked potentials recorded for clinical assessment

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    Auditory evoked potential (AEP) recordings often require subjects to ignore the stimuli and stay awake. In the present experiment, early (ABR), middle (MLR), and late latency (LLR) AEPs were recorded to compare the effect of five different distracting tasks: (1) doing nothing eyes open, (2) reading, (3) watching a movie, (4) solving a three-digit sum, and (5) doing nothing eyes closed (or counting the stimuli for LLR). Results showed that neither the amplitudes nor the latencies of the ABR, MLR, or LLR were affected by task. However, the amount of pre-stimulus activity (noise) or amplitude rejection was significantly and differently affected by the distracting task. For the ABR, the math task was the noisiest but, for the MLR, the amount of noise was greater when watching a movie. As for the LLR, reading and watching a movie yielded the lowest percentage of rejected traces. In conclusion, the choice of distracting task depends on the AEP being measured and should be chosen to improve the quality of the AEP traces and thus reduce recording tim

    Condensin is required for chromosome arm cohesion during mitosis

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    We describe a novel requirement for the condensin complex in sister chromatid cohesion in Saccharomyces cerevisiae. Strikingly, condensin-dependent cohesion can be distinguished from cohesin-based pairing by a number of criteria. First, condensin is required to maintain cohesion at several chromosomal arm sites but, in contrast to cohesin, is not required at either centromere or telomere-proximal loci. Second, condensin-dependent interlinks are established during mitosis independently of DNA replication and are reversible within a single cell cycle. Third, the loss of condensin-dependent linkages occurs without affecting cohesin levels at the separated URA3 locus. We propose that, during mitosis, robust sister chromatid cohesion along chromosome arms requires both condensinand cohesin-dependent mechanisms, which function independently of each other. We discuss the implications of our results for current models of sister chromatid cohesion
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