Search results for "cycle"
showing 10 items of 3119 documents
Regulation of ribonucleotide reductase in response to iron deficiency
2011
Ribonucleotide reductase (RNR) is an essential enzyme required for DNA synthesis and repair. Although iron is necessary for class Ia RNR activity, little is known about the mechanisms that control RNR in response to iron deficiency. In this work, we demonstrate that yeast cells control RNR function during iron deficiency by redistributing the Rnr2–Rnr4 small subunit from the nucleus to the cytoplasm. Our data support a Mec1/Rad53-independent mechanism in which the iron-regulated Cth1/Cth2 mRNA-binding proteins specifically interact with the WTM1 mRNA in response to iron scarcity, and promote its degradation. The resulting decrease in the nuclear-anchoring Wtm1 protein levels leads to the re…
The DNA-binding subunit p140 of replication factor C is upregulated in cycling cells and associates with G 1 phase cell cycle regulatory proteins
1999
The DNA-binding subunit of replication factor C (RFCp140) plays an important role in both DNA replication and DNA repair. The mechanisms regulating activation of RFCp140 thereby controlling replication and cellular proliferation are largely unknown. We analyzed protein expression of RFCp140 during cell cycle progression and investigated the association of RFCp140 with cell cycle regulatory proteins in cell lines of various tissue origin and in primary hematopoietic cells. Western and Northern blot analyses of RFCp140 from synchronized cells showed downregulation of RFCp140 when cells enter a G0-like quiescent state and upregulation of RFCp140 in cycling cells. Translocation from the cytopla…
Molecular basis of the functional distinction between Cln1 and Cln2 cyclins
2012
Cln1 and Cln2 are very similar but not identical cyclins. In this work, we tried to describe the molecular basis of the functional distinction between Cln1 and Cln2. We constructed chimeric cyclins containing different fragments of Cln1 and Cln2 and performed several functional analysis that make it possible to distinguish between Cln1 or Cln2. We identified that region between amino acids 225 and 299 of Cln2 is not only necessary but also sufficient to confer Cln2 specific functionality compared with Cln1. We also studied Cln1 and Cln2 subcellular localization identifying additional differences between them. Both cyclins are distributed between the nucleus and the cytoplasm, but Cln1 shows…
Cell Cycle Activation of the Swi6p Transcription Factor Is Linked to Nucleocytoplasmic Shuttling
2003
The control of the subcellular localization of cell cycle regulators has emerged as a crucial mechanism in the regulation of cell division. In the present work, we have characterized the function of the karyopherin Msn5p in the control of the cell cycle of Saccharomyces cerevisiae. Phenotypic analysis of the msn5 mutant revealed an increase in cell size and a functional interaction between Msn5p and the cell cycle transcription factor SBF (composed of the Swi4p and Swi6p proteins), indicating that Msn5p is involved in Start control. In fact, we have shown that the level of Cln2p protein is drastically reduced in an msn5 mutant. The effect on CLN2 expression is mediated at a transcriptional …
Amyloid Precursor-like Protein 1 Influences Endocytosis and Proteolytic Processing of the Amyloid Precursor Protein
2005
Ectodomain shedding of the amyloid precursor protein (APP) is a key regulatory step in the generation of the Alzheimer disease amyloid beta peptide (Abeta). The molecular mechanisms underlying the control of APP shedding remain little understood but are in part dependent on the low density lipoprotein receptor-related protein (LRP), which is involved in APP endocytosis. Here, we show that the APP homolog APLP1 (amyloid precursor-like protein 1) influences APP shedding. In human embryonic kidney 293 cells expression of APLP1 strongly activated APP shedding by alpha-secretase and slightly reduced beta-secretase cleavage. As revealed by domain deletion analysis, the increase in APP shedding re…
A comparison of cytoplasmic and nuclear estradiol and progesterone receptors in human fallopian tube and endometrial tissue
1981
Quantitative and qualitative aspects of the in vitro binding of 3 H-estradiol and 3 H-progesterone to receptor components from human endometrium and fallopian tube cytoplasmic and nuclear fractions were studied. The steroid binding macromolecules formed in vitro could be extracted from nuclei by 0.4M KCl and detected by glycerol gradient centrifugation. Both estradiol- and progesterone-binding compounds formed only one peak (under high ionic strength conditions) with a sedimentation coefficient of about 4-5S. The number of cytoplasmic and nuclear binding sites for both estradiol and R5020 varied dramatically throughout the menstrual cycle: the estradiol and progesterone receptor concentrati…
Cutting edge: priming of CTL by transcutaneous peptide immunization with imiquimod.
2005
Abstract CTL are important in combating cancer and viruses. Therefore, triggering the complete potential of CTL effector functions by new vaccination strategies will not only improve prophylaxis of tumor or virus-related diseases, but also open opportunities for effective therapeutic immunizations. Using transcutaneous immunization, we show that epicutaneous (e.c.)4 application of an ointment containing a CTL epitope and the TLR7 ligand imiquimod is highly effective in activating T cells in mice using TCR-transgenic CTL or in wild-type mice. Transcutaneous immunization-activated CTL mount a full-blown immune response against the target epitope characterized by proliferation, cytolytic activ…
H-2-linked murine cytotoxic T cell responses specific for sendai virus-infected cells
1978
CBA (H-2k) mouse-derived lymphochoriomeningitis virus and herpes simplex virus-specific cytotoxic T lymphocytes lyse virus-infected target cells compatible on either the H-2k or H-2D region. In contrast, CBA, C3H and AKR (H-2k) mouse-derived sendai virus-specific cytotoxic T lymphocytes (CTL) fail to lyse H-2D-compatible virus-infected cells. A similar lack of H-2D region-associated lytic activity was found with C57BL/6 and C57BL/10 (H-2b) mice as well as with the recombinants B10.A (2R) [Kb-Db] and B10.A (4R) [Kk-Db]. On the other hand, BALB/c (H-2d) mice and A/J (H-2a) mice do generate H-2Dd-associated sendai virus-specific CTL. These results are in contrast to those obtained with (CBA X …
Virion Antigens Introduced Exogeneously into the Cell Membrane Render Syngeneic Target Cells Susceptible for T Cell-Mediated Cytolysis
1977
Non-infectious sendai virus renders H-2 matched target cells susceptible to the lytic effect of sendai virus immune cytotoxic T lymphocytes. This observation suggests that exogeneous insertion of virion antigen in the membrane of the target cell is sufficient for T cell cytotoxicity. The finding is incompatible with the concept that H-2K or H-2D gene products of the target cells must be altered in their primary structure (pretranslational effect of the virus infection) for T cell-mediated cytolysis to occur.
Fine specificity and cytolytic activity of continuously growing alloreactive cytotoxic T lymphocyte clones.
1980
The role of Lyt 1+ T-cell-derived secondard CTL inducing factor allowed the cloning of alloreactive cytotoxic T lymphocytes (CTL) by the limiting dilution approach. Several monoclonal cell lines were established in vitro. The lytic activity of some of the cell lines exceeded that of CTL from bulk cultures; that is, 50% of the target cells were lysed at an effector to target cell ratio of 0.04:1. The fine specificity of individual CTL clones is discussed.