KDM2A represses transcription of centromeric satellite repeats and maintains the heterochromatic state

Heterochromatin plays an essential role in the preservation of epigenetic information, the transcriptional repression of repeti- tive DNA elements and inactive genes, and the proper segregation of chromosomes during mitosis. Here we identify KDM2A, a JmjC-domain containing histone demethylase, as a heterochro- matin-associated and HP1-interacting protein that promotes HP1 localization to chromatin. We show that KDM2A is required to maintain the heterochromatic state, as determined using a candidate-based approach coupled to an in vivo epigenetic reporter system. Remarkably, a parallel and independent siRNA screen also detected a role for KDM2A in epigenetic silencing. Moreover, we demonstrate that KDM2A associates with centromeres and represses transcription of small non-coding RNAs that are encoded by the clusters of satellite repeats at the centromere. Dissecting the relationship between heterochromatin and centromeric RNA transcription is the basis of ongoing studies. We demonstrate that forced expression of these satellite RNA transcripts compromise the heterochromatic state and HP1 localization to chromatin. Finally, we show that KDM2A is required to sustain centromeric integ- rity and genomic stability, particularly during mitosis. Since the disruption of epigenetic control mechanisms contributes to cellular transformation, these results, together with the low levels of KDM2A found in prostate carcinomas, suggest a role for KDM2A in cancer development

Regulation of calpain-1 signaling in platelets.

Regulation of calpain-1 signaling in platelets

NS5A Promotes Constitutive Degradation of IP3R3 to Counteract Apoptosis Induced by Hepatitis C Virus

FBXL2 targets IP3R3 for ubiquitin-mediated degradation to limit Ca2+ flux to mitochondria and, consequently, apoptosis. Efficient replication of hepatitis C virus (HCV) requires geranylgeranylation of FBXL2. Here, we show that the viral protein NS5A forms a trimeric complex with IP3R3 and FBXL2, unmasking IP3R3’s degron in the absence of inositol 1,4,5-trisphosphate (IP3) stimulation. FBXL2 knockdown or expression of a stable IP3R3 mutant causes persistent Ca2+ flux and sensitizes cells to apoptosis, resulting in the inhibition of viral replication. Importantly, the effect of FBXL2 silencing is rescued by depleting IP3R3, but not p85β another established FBXL2 substrate, indicating that the anti-HCV effect of FBXL2 knockdown is largely due to IP3R3 stabilization. Finally, disruption of the FBXL2-NS5A-IP3R3 complex using somatic cell genetics or pharmacologic inhibition results in IP3R3 stabilization and suppression of HCV replication. This study reveals an IP3-independent molecular mechanism through which HCV promotes IP3R3 degradation, thereby inhibiting virus-induced apoptosis and establishing chronic infection. Kuchay et al. show that the HCV NS5A protein forms a complex with IP3R3 and FBXL2 and promotes constitutive FBXL2-mediated degradation of IP3R3. IP3R3 degradation inhibits calcium flux, mitochondrial calcium overload, and apoptosis. Thus, NS5A contributes to a cellular environment that is permissive for chronic HCV infection

Incidence of primary hypothyroidism in patients exposed to therapeutic external beam radiation, where radiation portals include a part or whole of the thyroid gland

Introduction: Hypothyroidism is a known consequence of external-beam radiotherapy to the neck encompassing a part or whole of the thyroid gland. In this non-randomized prospective study, we have tried to evaluate the response of the thyroid gland to radiation by assessing thyroid function before irradiation and at regular intervals after irradiation. Aims and Objectives: The aim of this study were to assess in the cancer patients, who were exposed to the therapeutic external beam radiation, where radiation portals include a part or whole of the thyroid gland: the incidence of primary hypothyroidism, the time required to become hypothyroid, any relation between the total dose for the development of hypothyroidism, and whether there are any patient or treatment-related factors that are predictive for the development of hypothyroidism, including the use of concurrent chemotherapy. Materials and Methods: This non-randomized, prospective study was conducted for a period of 2 years in which thyroid function was assessed in 59 patients (cases) of head and neck cancer, breast cancer, lymphoma patients and other malignancies, who had received radiotherapy to the neck region. 59 euthyroid healthy patients (controls) were also taken, who had not received the neck irradiation. These patients/controls were assessed periodically for 2 years. Results: The incidence of hypothyroidism after external beam radiation therapy (EBRT) to neck where radiation portals include part or whole of the thyroid gland was 16.94%, seven cases had subclinical hypothyroidism (11.86%) and three cases had clinical hypothyroidism (5.08%). Mean time for development of hypothyroidism was 4.5 months. There was no effect of age, gender, primary tumor site, radiation dose and chemotherapy, whether neoadjuvant or concurrent with the development of hypothyroidism. Conclusion: In summary, we found that thyroid dysfunction is a prevalent, yet easily treatable source of morbidity in patients undergoing radiation therapy to neck where radiation portals include a part or whole of the thyroid gland

Double Knockouts Reveal that Protein Tyrosine Phosphatase 1B Is a Physiological Target of Calpain-1 in Platelets▿

Calpains are ubiquitous calcium-regulated cysteine proteases that have been implicated in cytoskeletal organization, cell proliferation, apoptosis, cell motility, and hemostasis. Gene targeting was used to evaluate the physiological function of mouse calpain-1 and establish that its inactivation results in reduced platelet aggregation and clot retraction potentially by causing dephosphorylation of platelet proteins. Here, we report that calpain-1 null (Capn1−/−) platelets accumulate protein tyrosine phosphatase 1B (PTP1B), which correlates with enhanced tyrosine phosphatase activity and dephosphorylation of multiple substrates. Treatment of Capn1−/− platelets with bis(N,N-dimethylhydroxamido)hydroxooxovanadate, an inhibitor of tyrosine phosphatases, corrected the aggregation defect and recovered impaired clot retraction. More importantly, platelet aggregation, clot retraction, and tyrosine dephosphorylation defects were rescued in the double knockout mice lacking both calpain-1 and PTP1B. Further evaluation of mutant mice by the ferric chloride-induced arterial injury model suggests that the Capn1−/− mice are relatively resistant to thrombosis in vivo. Together, our results demonstrate that PTP1B is a physiological target of calpain-1 and suggest that a similar mechanism may regulate calpain-1-mediated tyrosine dephosphorylation in other cells

Association of polycystic ovary syndrome and Graves′ disease: Is autoimmunity the link between the two diseases

Introduction: Polycystic ovary syndrome (PCOS) is a common endocrinopathy of women of child-bearing age. Although some studies have suggested an association between PCOS and autoimmune thyroiditis, to our knowledge, only a few cases indicating association between PCOS and Graves′ disease are reported. Objective: We aim to describe this first case series of six women presenting with PCOS and Graves′ disease together. Materials and Methods: Women attending the endocrinology clinic at a tertiary care centre in north India and fulfilling the AE-PCOS criteria for diagnosis of PCOS were studied using a predefined proforma for any clinical, biochemical and imaging features of Graves′ disease. Results: The series consisted of six women with a mean age of 27.5 years and menarche as 12.6 years. All women were lean with mean BMI of 22.73 kg / m 2 and three out of six had waist circumference <80 cm. The mean FG score of subjects was 16.66 and average total testosterone was 77.02 ng / dl (25.0-119.64). All the patients had suppressed TSH, the average being 0.052 μIU/ml (0.01-0.15). Thyroid gland was enlarged in all clinically and on ultrasonography and imaging with 99m Tc and/or RAIU revealed diffuse increased uptake. Conclusions: The association of a rare disorder like Graves′ disease with a relatively common disorder like PCOS is unlikely to be because of a chance alone and may point to a common aetiopathogenic linkage leaving a scope for molecular characterization

Targeted Gene Inactivation of Calpain-1 Suppresses Cortical Degeneration Due to Traumatic Brain Injury and Neuronal Apoptosis Induced by Oxidative Stress*

Calpains are calcium-regulated cysteine proteases that have been implicated in the regulation of cell death pathways. Here, we used our calpain-1 null mouse model to evaluate the function of calpain-1 in neural degeneration following a rodent model of traumatic brain injury. In vivo, calpain-1 null mice show significantly less neural degeneration and apoptosis and a smaller contusion 3 days post-injury than wild type littermates. Protection from traumatic brain injury corroborated with the resistance of calpain-1 neurons to apoptosis induced by oxidative stress. Biochemical analysis revealed that caspase-3 activation, extracellular calcium entry, mitochondrial membrane permeability, and release of apoptosis-inducing factor from mitochondria are partially blocked in the calpain-1 null neurons. These findings suggest that the calpain-1 knock-out mice may serve as a useful model system for neuronal protection and apoptosis in traumatic brain injury and other neurodegenerative disorders in which oxidative stress plays a role