Ribonuclease Activity of Dis3 Is Required for Mitotic Progression and Provides a Possible Link between Heterochromatin and Kinetochore Function

BACKGROUND: Cellular RNA metabolism has a broad range of functional aspects in cell growth and division, but its role in chromosome segregation during mitosis is only poorly understood. The Dis3 ribonuclease is a key component of the RNA-processing exosome complex. Previous isolation of the dis3-54 cold-sensitive mutant of fission yeast Schizosaccharomyces pombe suggested that Dis3 is also required for correct chromosome segregation. METHODOLOGY/PRINCIPAL FINDINGS: We show here that the progression of mitosis is arrested in dis3-54, and that segregation of the chromosomes is blocked by activation of the mitotic checkpoint control. This block is dependent on the Mad2 checkpoint protein. Double mutant and inhibitor analyses revealed that Dis3 is required for correct kinetochore formation and function, and that this activity is monitored by the Mad2 checkpoint. Dis3 is a member of the highly conserved RNase II family and is known to be an essential subunit of the exosome complex. The dis3-54 mutation was found to alter the RNaseII domain of Dis3, which caused a reduction in ribonuclease activity in vitro. This was associated with loss of silencing of an ura4(+) reporter gene inserted into the outer repeats (otr) and central core (cnt and imr) regions of the centromere. On the other hand, centromeric siRNA maturation and formation of the RITS RNAi effector complex was normal in the dis3-54 mutant. Micrococcal nuclease assay also suggested the overall chromatin structure of the centromere was not affected in dis3-54 mutant. CONCLUSIONS/SIGNIFICANCE: RNase activity of Dis3, a core subunit of exosome, was found to be required for proper kinetochore formation and establishment of kinetochore-microtubule interactions. Moreover, Dis3 was suggested to contribute to kinetochore formation through an involvement in heterochromatic silencing at both outer centromeric repeats and within the central core region. This activity is likely monitored by the mitotic checkpoint, and distinct from that of RNAi-mediated heterochromatin formation directly targeting outer centromeric repeats

Both osmolality-dependent and independent mechanisms are associated with acute hyperglycemia-induced cardiovascular adverse reactions: Analysis of the mutual interactions leading to cardiovascular phenotypes in dogs.

Acute hyperglycemia causes various cardiovascular responses; however, the underlying pathophysiology in vivo is myriad and complex, of which mutual interactions remain poorly understood. We analyzed the cardiovascular effects of acute hyperglycemia in comparison with those of hyperosmolality alone. Three g/kg of D-glucose (n = 4) or D-mannitol (n = 4) was intravenously infused to isoflurane-anesthetized intact dogs. Glucose infusion increased plasma glucose level and osmolality, whereas mannitol infusion similarly changed osmolality to glucose infusion but decreased glucose level. Glucose infusion decreased total peripheral vascular resistance, but increased heart rate, left ventricular contraction, left ventricular preload and cardiac output without altering mean blood pressure. Mannitol infusion likewise changed them, but its positive chronotropic and inotropic effects were less potent than those of glucose infusion. Glucose infusion prolonged PR interval, QRS width and QTcV. Mannitol infusion similarly changed them, but its QTcV prolongation was smaller than that of glucose infusion. Glucose infusion-induced cardiovascular responses would be basically attributed to osmolality-dependent mechanisms, whereas its positive chronotropic and inotropic effects along with repolarization delay may be enhanced by osmolality-independent mechanisms, including hyperglycemia by itself and insulin release

Early molecular response predicts outcomes in patients with chronic myeloid leukemia in chronic phase treated with frontline nilotinib or imatinib

We explored the impact of early molecular response (EMR; BCR-ABL ≤10% on the international scale [BCR-ABL(IS)] at 3 or 6 months) on outcomes in patients with newly diagnosed chronic myeloid leukemia in chronic phase treated with nilotinib or imatinib based on 4 years of follow up in Evaluating Nilotinib Efficacy and Safety in Clinical Trials-Newly Diagnosed Patients. Patients (n = 846) received nilotinib 300 mg twice daily, nilotinib 400 mg twice daily, or imatinib 400 mg once daily. At 3 months, more patients had EMR failure (ie, BCR-ABL(IS) >10%) on imatinib (33%) than on nilotinib (9%-11%); similarly at 6 months, 16% of patients in the imatinib arm vs 3% and 7% in the nilotinib arms had EMR failure. In all arms, EMR failure was associated with lower rates of molecular response, an increased risk of progression, and lower overall survival compared with EMR achievement. We also analyzed patient and treatment characteristics associated with EMR and found distinct patterns in the nilotinib arms vs the imatinib arm. High Sokal risk score was associated with a high rate of EMR failure on imatinib, but not on nilotinib. In contrast, reduced dose intensity and dose interruptions were strongly associated with EMR failure in nilotinib-treated, but not imatinib-treated, patients. This study is registered at www.clinicaltrials.gov as #NCT00471497.Timothy P. Hughes, Giuseppe Saglio, Hagop M. Kantarjian, François Guilhot, Dietger Niederwieser, Gianantonio Rosti, Chiaki Nakaseko, Carmino Antonio De Souza, Matt E. Kalaycio, Stephan Meier, Xiaolin Fan, Hans D. Menssen, Richard A. Larson, and Andreas Hochhau