hMSH5 Facilitates the Repair of Camptothecin-induced Double-strand Breaks through an Interaction with FANCJ

Replication stress from stalled or collapsed replication forks is a major challenge to genomic integrity. The anticancer agent camptothecin (CPT) is a DNA topoisomerase I inhibitor that causes fork collapse and double-strand breaks amid DNA replication. Here we report that hMSH5 promotes cell survival in response to CPT-induced DNA damage. Cells deficient in hMSH5 show elevated CPT-induced γ-H2AX and RPA2 foci with concomitant reduction of Rad51 foci, indicative of impaired homologous recombination. In addition, CPT-treated hMSH5-deficient cells exhibit aberrant activation of Chk1 and Chk2 kinases and therefore abnormal cell cycle progression. Furthermore, the hMSH5-FANCJ chromatin recruitment underlies the effects of hMSH5 on homologous recombination and Chk1 activation. Intriguingly, FANCJ depletion desensitizes hMSH5-deficient cells to CPT-elicited cell killing. Collectively, our data point to the existence of a functional interplay between hMSH5 and FANCJ in double-strand break repair induced by replication stress.     

TIMP-2 fusion protein with human serum albumin potentiates anti-angiogenesis-mediated inhibition of tumor growth by suppressing MMP-2 expression

TIMP-2 protein has been intensively studied as a promising anticancer candidate agent, but the in vivo mechanism underlying its anticancer effect has not been clearly elucidated by previous works. In this study, we investigated the mechanism underlying the anti-tumor effects of a TIMP-2 fusion protein conjugated with human serum albumin (HSA/TIMP-2). Systemic administration of HSA/TIMP-2 effectively inhibited tumor growth at a minimum effective dose of 60 mg/kg. The suppressive effect of HSA/TIMP-2 was accompanied by a marked reduction of in vivo vascularization. The anti-angiogenic activity of HSA/TIMP-2 was directly confirmed by CAM assays. In HSA/TIMP-2-treated tumor tissues, MMP-2 expression was profoundly decreased without a change in MT1-MMP expression of PECAM-1-positive cells. MMP-2 mRNA was also decreased by HSA/TIMP-2 treatment of human umbilical vein endothelial cells. Zymographic analysis showed that HSA/TIMP-2 substantially decreased extracellular pro-MMP-2 activity (94-99% reduction) and moderately decreased active MMP-2 activity (10-24% reduction), suggesting MT1-MMP-independent MMP-2 modulation. Furthermore, HSA/TIMP-2 had no effect on in vitro active MMP-2 activity and in vivo MMP-2 activity. These studies show that HSA/TIMP-2 potentiates anti-angiogenic activity by modulating MMP-2 expression, but not MMP-2 activity, to subsequently suppress tumor growth, suggesting an important role for MMP-2 expression rather than MMP-2 activity in anti-angiogenesis.     

Structure and magnetic properties of LnIII[Ru2(CO3)4] · 8H2O

Ln^III[Ru₂(CO₃)₄] · 8H₂O (Ln = Gd, Nd, Ho, Yb) is formed from the reaction of Ln^III and [Ru₂(CO₃)₄]^3? in water. These Ln^III materials have a 3D network structure composed of linked chains and μ_n-CO₃ linkages to both Ru and Ln^III sites, and are best described as Ln^III(OH₂)₄[Ru₂(CO₃)₄]_1/2[Ru₂(CO₃)₄(OH₂)₂]_1/2 · 3H₂O. Complete characterization of the Gd^III species is presented, as the other Ln^III are isostructural and exhibit large spin–orbit coupling leading to complex magnetic behavior. Magnetic ordering is not observed above 2 K.     

Novel roles for protein kinase Cdelta-dependent signaling pathways in acute hypoxic stress-induced autophagy

Macroautophagy, a tightly orchestrated intracellular process for bulk degradation of cytoplasmic proteins or organelles, is believed to be essential for cell survival or death in response to stress conditions. Recent observations indicate that autophagy is an adaptive response in cells subjected to prolonged hypoxia. However, the signaling mechanisms that activate autophagy under acute hypoxic stress are not clearly understood. In this study, we show that acute hypoxic stress by treatment with 1% O(2) or desferroxamine, a hypoxia-mimetic agent, of cells renders a rapid induction of LC3-II level changes and green fluorescent protein-LC3 puncta accumulation, hallmarks of autophagic processing, and that this process involves protein kinase Cdelta (PKCdelta), and occurs prior to the induction of BNIP3 (Bcl-2/adenovirus E1B 19-kDa interacting protein 3). Interestingly, hypoxic stress leads to a rapid and transient activation of JNK in Pa-4 or mouse embryo fibroblast cells. Acute hypoxic stress-induced changes in LC3-II level and JNK activation are attenuated in Pa-4 cells by dominant negative PKCdeltaKD or in mouse embryo fibroblast/PKCdelta-null cells. Intriguingly, the requirement of PKCdelta is not apparent for starvation-induced autophagy. The importance of PKCdelta in hypoxic stress-induced adaptive responses is further supported by our findings that inhibition of PKCdelta-facilitated autophagy by 3-methyladenine or Atg5 knock-out renders a greater prevalence of cell death following prolonged desferroxamine treatment, whereas PKCdelta- or JNK1-deficient cells exhibit resistance to extended hypoxic exposure. These results uncover dual roles of PKCdelta-dependent signaling in the cell fate determination upon hypoxic exposure.     

Unique expression of a small IL-32 protein in the Jurkat leukemic T cell line

Interleukin (IL)-32 was recently identified as a new cytokine which induces various proinflammatory cytokines in human monocytes and macrophages. Therefore, IL-32 has been primarily studied in inflammatory models such as rheumatoid arthritis and inflammatory bowel diseases. The regulation of endogenous IL-32 in other immune cells remains unknown. In the present study, we stimulated Jurkat T cells with phytohaemagglutinin (PHA) and phorbol myristate acetate (PMA) and examined IL-32 expression at both the mRNA and protein levels. All mRNAs of the four IL-32 isoforms and the 12-15 kDa IL-32 protein were independent of PHA and PMA stimulation, however a 9 kDa molecular weight IL-32 protein in the cell culture supernatant was induced by PHA and PMA after 16 h of stimulation. Compared to other human cell lines, the Jurkat cell line constitutively expressed a 12-15 kDa molecule of IL-32, which is smaller than the known IL-32 isoforms. We used IL-32 shRNA to examine the specificity of the 12-15 kDa molecule. Upon IL-32 shRNA transfection, the 12-15 kDa band was decreased specifically as compared to the control scrambled clone. Thus, the constitutive expression of IL-32 mRNA as well as the predominant production of a smaller sized IL-32 isoform in Jurkat cells may implicate a role for IL-32 in human T cell leukemia.