Regulation of p53 Translation and Induction after DNA Damage by Ribosomal Protein L26 and Nucleolin

SummaryIncreases in p53 protein levels after DNA damage have largely been attributed to an increase in the half-life of p53 protein. Here we demonstrate that increased translation of p53 mRNA is also a critical step in the induction of p53 protein in irradiated cells. Ribosomal protein L26 (RPL26) and nucleolin were found to bind to the 5′ untranslated region (UTR) of p53 mRNA and to control p53 translation and induction after DNA damage. RPL26 preferentially binds to the 5′UTR after DNA damage, and its overexpression enhances association of p53 mRNA with heavier polysomes, increases the rate of p53 translation, induces G1 cell-cycle arrest, and augments irradiation-induced apoptosis. Opposite effects were seen when RPL26 expression was inhibited. In contrast, nucleolin overexpression suppresses p53 translation and induction after DNA damage, whereas nucleolin downregulation promotes p53 expression. These findings demonstrate the importance of increased translation of p53 in DNA-damage responses and suggest critical roles for RPL26 and nucleolin in affecting p53 induction

Calcium-Dependent Protein Kinase 5 Is Required for Release of Egress-Specific Organelles in Plasmodium falciparum

ABSTRACT The human malaria parasite Plasmodium falciparum requires efficient egress out of an infected red blood cell for pathogenesis. This egress event is highly coordinated and is mediated by several signaling proteins, including the plant-like P. falciparum calcium-dependent protein kinase 5 (PfCDPK5). Knockdown of PfCDPK5 results in an egress block where parasites are trapped inside their host cells. The mechanism of this PfCDPK5-dependent block, however, remains unknown. Here, we show that PfCDPK5 colocalizes with a specialized set of parasite organelles known as micronemes and is required for their discharge, implicating failure of this step as the cause of the egress defect in PfCDPK5-deficient parasites. Furthermore, we show that PfCDPK5 cooperates with the P. falciparum cGMP-dependent kinase (PfPKG) to fully activate the protease cascade critical for parasite egress. The PfCDPK5-dependent arrest can be overcome by hyperactivation of PfPKG or by physical disruption of the arrested parasite, and we show that both treatments facilitate the release of the micronemes required for egress. Our results define the molecular mechanism of PfCDPK5 function and elucidate the complex signaling pathway of parasite egress

Effects of Darunavir/Ritonavir-Based Therapy on Metabolic and Anthropometric Parameters in Women and Men Over 48 Weeks

Gender-based differences in lipids have been noted in antiretroviral clinical trials. We present the metabolic and anthropometric data from the GRACE (Gender, Race And Clinical Experience) study by gender. Treatment-experienced adults received darunavir/ritonavir (DRV/r) 600/100 mg twice daily, plus a background regimen, over 48 weeks. Fasting blood samples were obtained for lipid, glucose, and insulin measurements at baseline and at weeks 24 and 48/early discontinuation. Anthropometric measurements were taken at baseline and at weeks 12, 24, and 48/discontinuation. The Assessment of Body Change and Distress questionnaire was administered at baseline and regular intervals. Descriptive statistics as well as comparisons using a Wilcoxon rank-sum test are reported. Four hundred twenty-nine patients (women, n=287; men, n=142) enrolled in GRACE; 94 women (32.8%) and 33 men (23.2%) discontinued the trial. Median changes in triglycerides from baseline to week 48 were higher in men (25 mg/dL versus 8 mg/dL; p=0.006); the mean change in triglycerides was higher in men than in women in all racial subgroups. Other lipid and glucose level changes were similar between genders. Anthropometric parameters increased for both genders, with larger increases in women. Patients' perceptions of body changes concurred with physical measurements. The proportion of women who were “satisfied” or “very satisfied” with their bodies increased from 45.2% to 57.8% from baseline to week 48 (p=0.005), while the proportion of men who were “satisfied” or “very satisfied” with their bodies increased from 56.3% to 61.5% from baseline to week 48 (p=0.317). DRV/r-based therapy was associated with small to moderate changes in metabolic parameters, and few between-gender differences were observed. Levels of self-reported, body-related distress improved for women and men over 48 weeks

A phase 1 study of the CXCR4 antagonist plerixafor in combination with high-dose cytarabine and etoposide in children with relapsed or refractory acute leukemias or myelodysplastic syndrome: a pediatric oncology experimental therapeutics investigators\u27 consortium study (POE 10-03).

BACKGROUND: Plerixafor, a reversible CXCR4 antagonist, inhibits interactions between leukemic blasts and the bone marrow stromal microenvironment and may enhance chemosensitivity. A phase 1 trial of plerixafor in combination with intensive chemotherapy in children and young adults with relapsed or refractory acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), and myelodysplastic syndrome (MDS) was performed to determine a tolerable and biologically active dose. PROCEDURE: Plerixafor was administered daily for 5 days at four dose levels (6, 9, 12, and 15 mg/m RESULTS: Nineteen patients (13 with AML, 5 with ALL, 1 with MDS) were treated. The most common grade 3 or greater nonhematologic toxicities attributable to plerixafor were febrile neutropenia and hypokalemia. There were no dose-limiting toxicities (DLTs). Plerixafor exposure increased with increasing dose levels and clearance was similar on days 1 and 5. Eighteen patients were evaluable for response. Two patients achieved complete remission (CR) and one patient achieved CR with incomplete hematologic recovery (CRi): all three had AML. No responses were seen in patients with ALL or MDS. Plerixafor mobilized leukemic blasts into the peripheral blood in 14 of 16 evaluable patients (median 3.4-fold increase), and the degree of mobilization correlated with surface CXCR4 expression. CONCLUSIONS: Plerixafor, in combination with high-dose cytarabine and etoposide, was well tolerated in children and young adults with relapsed/refractory acute leukemias and MDS. While biologic responses were observed, clinical responses in this heavily pretreated cohort were modest