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31.
Gemmell NJ Sin FY 《BioEssays : news and reviews in molecular, cellular and developmental biology》2002,24(3):275-279
The human Y chromosome contains very low levels of nucleotide variation. It has been variously hypothesized that this invariance reflects historic reductions in the human male population, a very recent common ancestry, a slow rate of molecular evolution, an inability to evolve adaptively, or frequent selective sweeps acting on genes borne on the Y chromosome. We propose an alternative theory in which human Y chromosome evolution is driven by mutations in the maternally inherited mitochondrial genome, which impair male fertility and ultimately lead to a reduction in the effective population size (N(e)) and consequently the variability of the Y chromosome. 相似文献
32.
The lytic cycle of Epstein-Barr virus is associated with decreased expression of cell surface major histocompatibility complex class I and class II molecules 下载免费PDF全文
Human herpesviruses utilize an impressive range of strategies to evade the immune system during their lytic replicative cycle, including reducing the expression of cell surface major histocompatibility complex (MHC) and immunostimulatory molecules required for recognition and lysis by virus-specific cytotoxic T cells. Study of possible immune evasion strategies by Epstein-Barr virus (EBV) in lytically infected cells has been hampered by the lack of an appropriate permissive culture model. Using two-color immunofluorescence staining of cell surface antigens and EBV-encoded lytic cycle antigens, we examined EBV-transformed B-cell lines in which a small subpopulation of cells had spontaneously entered the lytic cycle. Cells in the lytic cycle showed a four- to fivefold decrease in cell surface expression of MHC class I molecules relative to that in latently infected cells. Expression of MHC class II molecules, CD40, and CD54 was reduced by 40 to 50% on cells in the lytic cycle, while no decrease was observed in cell surface expression of CD19, CD80, and CD86. Downregulation of MHC class I expression was found to be an early-lytic-cycle event, since it was observed when progress through late lytic cycle was blocked by treatment with acyclovir. The immediate-early transactivator of the EBV lytic cycle, BZLF1, did not directly affect expression of MHC class I molecules. However, BZLF1 completely inhibited the upregulation of MHC class I expression mediated by the EBV cell-transforming protein, LMP1. This novel function of BZLF1 elucidates the paradox of how MHC class I expression can be downregulated when LMP1, which upregulates MHC class I expression in latent infection, remains expressed in the lytic cycle. 相似文献
33.
Comparison of responses elicited by immunization with a Legionella species common lipoprotein delivered as naked DNA or recombinant protein 总被引:5,自引:0,他引:5
To evaluate the peptidoglycan-associated lipoprotein (PAL) antigen of Legionella pneumophila as a vaccine candidate, mice were immunized intramuscularly with pcDNA3-PAL and intraperitoneally with recombinant PAL (t-rPAL), which were compared for their ability to induce PAL-specific immune responses. The t-rPAL protein induced PAL-specific IgG antibody production significantly more than did pcDNA3-PAL. The IgG2a and IgG1 production was predominant after pcDNA3-PAL and t-rPAL administration, respectively. In particular, pcDNA3-PAL induced much higher PAL-specific cytotoxic T-lymphocyte responses than did t-rPAL. Furthermore, in vivo, CD19+ B-cell populations were dramatically increased by t-rPAL vaccination, suggesting a B-cell immunomodulatory activity of the lipoprotein. The PAL antigen was also conserved among Legionella species, as determined by PCR and immunoblot analyses. These results support a potential use of the t-rPAL protein and in particular DNA vaccines against Legionella infections. 相似文献
34.
Apoptosis induction in HL-60 cells and inhibition of topoisomerase II by triterpene celastrol 总被引:2,自引:0,他引:2
Nagase M Oto J Sugiyama S Yube K Takaishi Y Sakato N 《Bioscience, biotechnology, and biochemistry》2003,67(9):1883-1887
Celastrol, which is a triterpene purified from Celastraceae plants, has anticancer and anti-inflammatory activities. In this study we investigated to clarify whether celastrol can induce apoptosis in a human leukemia HL-60 model system. Celastrol was found to induce apoptosis, and the rank order of the potency of celastrol and its derivatives to induce internucleosomal DNA fragmentation was found to be celastrol>cela-H>the other derivatives=vehicle control. Many anticancer agents are known to possess the ability to inhibit topoisomerase II, so the inhibitory activities of celastrol and its derivatives on topoisomerase II were also explored. The rank order of the inhibitory activity was found to be celastrol>etoposide>cela-H, indicating that the apoptosis-inducing activities of cela derivatives correspond to their inhibitory activities on topoisomerase II. These data suggested that celastrol may cause its effects such as anticancer activity by the mechanism of apoptosis along with topoisomerase II inhibition. 相似文献
35.
The Saccharomyces cerevisiae YCC5 (YCL025c) Gene Encodes an Amino Acid Permease, Agp1, Which Transports Asparagine and Glutamine 下载免费PDF全文
The yeast YCC5 gene encodes a putative amino acid permease and is homologous to GNP1 (encoding a high-affinity glutamine permease). Using strains with disruptions in the genes for multiple permeases, we demonstrated that Ycc5 (which we have renamed Agp1) is involved in the transport of asparagine and glutamine, performed a kinetic analysis of this activity, and showed that AGP1 expression is subject to nitrogen repression. 相似文献
36.
A cereal cyst nematode (Heterodera avenae Woll.) resistance gene transferred from Aegilops triuncialis to hexaploid wheat 总被引:1,自引:0,他引:1
M. D. Romero M. J. Montes E. Sin I. Lopez-Braña A. Duce J. A. Martín-Sanchez M. F. Andrés A. Delibes 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(8):1135-1140
The cereal cyst nematode (Heterodera avenae) is an important root parasite of common wheat. A high level of resistance was transferred to wheat from Aegilops triuncialis (TR lines) using the cross [(T. turgidum×Ae. triuncialis)×T. aestivum]. Low fertility (3–5 viable kernels per plant) was observed during the process but the surviving hybrid plants were highly
vigorous. To obtain stable resistant lines further crosses to T. aestivum were performed. The resistance in TR lines seems to be transferred from the C genome of Ae. triuncialis (genomes CCUU). Ae. triuncialis was highly resistant to the two Spanish populations of H. avenae tested, as well as to four French races and two Swedish populations. The histological analysis showed a hypersensitive reaction
in the roots of a resistant TR line inoculated with the Ha71 pathotype of H. avenae, whereas well-formed syncytia were observed in the roots of the susceptible control. Resistance to the H. avenae Ha71 pathotype seemed to be inherited as determined by a single dominant factor in the crosses between resistant TR lines
and susceptible cultivars.
Received: 11 November 1997 / Accepted: 9 December 1997 相似文献
37.
RhoA-Binding Kinase α Translocation Is Facilitated by the Collapse of the Vimentin Intermediate Filament Network 下载免费PDF全文
Wun-Chey Sin Xiang-Qun Chen Thomas Leung Louis Lim 《Molecular and cellular biology》1998,18(11):6325-6339
The regulation of morphological changes in eukaryotic cells is a complex process involving major components of the cytoskeleton including actin microfilaments, microtubules, and intermediate filaments (IFs). The putative effector of RhoA, RhoA-binding kinase α (ROKα), is a serine/threonine kinase that has been implicated in the reorganization of actin filaments and in myosin contractility. Here, we show that ROKα also directly affects the structural integrity of IFs. Overexpression of active ROKα, like that of RhoA, caused the collapse of filamentous vimentin, a type III IF. A RhoA-binding-deficient, kinase-inactive ROKα inhibited the collapse of vimentin IFs induced by RhoA in HeLa cells. In vitro, ROKα bound and phosphorylated vimentin at its head-rod domain, thereby inhibiting the assembly of vimentin. ROKα colocalized predominantly with the filamentous vimentin network, which remained intact in serum-starved cells. Treatment of cells with vinblastine, a microtubule-disrupting agent, also resulted in filamentous vimentin collapse and concomitant ROKα translocation to the cell periphery. ROKα translocation did not occur when the vimentin network remained intact in vinblastine-treated cells at 4°C or in the presence of the dominant-negative RhoAN19 mutant. Transient translocation of ROKα was also observed in cells subjected to heat shock, which caused the disassembly of the vimentin network. Thus, the translocation of ROKα to the cell periphery upon overexpression of RhoAV14 or growth factor treatment is associated with disassembly of vimentin IFs. These results indicate that Rho effectors known to act on microfilaments may be involved in regulating the assembly of IFs. Vimentin when phosphorylated also exhibits reduced affinity for the inactive ROKα. The translocation of ROKα from IFs to the cell periphery upon action by activated RhoA and ROKα suggests that ROKα may initiate its own cascade of activation. 相似文献
38.
39.
Wei Zhen Chow Sin How Lim Lai Yee Ong Yean Kong Yong Yutaka Takebe Adeeba Kamarulzaman Kok Keng Tee 《PloS one》2015,10(9)
Human immunodeficiency virus type 1 (HIV-1) subtypes have been shown to differ in the rate of clinical progression. We studied the association between HIV-1 subtypes and the rate of CD4+ T-cell recovery in a longitudinal cohort of patients on combination antiretroviral therapy (cART). We studied 103 patients infected with CRF01_AE (69%) and subtype B (31%) who initiated cART between 2006 and 2013. Demographic data, CD4+ T-cell counts and HIV-1 viral load were abstracted from patient medical charts. Kaplan-Meier was used to estimate the time to CD4+ T-cell count increase to ≥350 between subtypes and effects of covariates were analysed using Cox proportional hazards. An 87% of the study population were male adults (mean age of 38.7 years old). Baseline CD4+ T-cell counts and viral loads, age at cART initiation, sex, ethnicity and co-infection did not differ significantly between subtypes. A shorter median time for CD4+ T-cell count increase to ≥350 cells/μL was observed for CRF01_AE (546 days; 95% confidence interval [CI], 186–906 days; P = .502) compared to subtype B (987 days; 95% CI, 894–1079 days). In multivariate analysis, female sex was significantly associated with a 2.7 times higher chance of achieving CD4+ T-cell recovery (adjusted hazard ratio [HR], 2.75; 95% CI, 1.21–6.22; P = .025) and both baseline CD4+ T-cell count (P = .001) and viral load (P = .001) were important predictors for CD4+ T-cell recovery. Immunological recovery correlated significantly with female sex, baseline CD4+ T-cell counts and viral load but not subtype. 相似文献
40.
Caroline Minassian Sara L. Thomas Liam Smeeth Ian Douglas Ruth Brauer Sinéad M. Langan 《PLoS medicine》2015,12(12)