Biomedical subjects

K van Zee

Publications and source records attributed to K van Zee.

10 recordsLinked to original sources

PubMed2000

Chest wall resection for locally recurrent breast cancer: is it worthwhile?

OBJECTIVE: The effectiveness of chest wall resection for locally recurrent breast cancer as cancer treatment remains poorly defined, possibly because of the general impression that locally recurrent disease is a harbinger of rapidly progressive metastatic disease and that extensive surgical treatment in these patients is inappropriate. Reports to date have focused on technical feasibility, not long-term outcome. METHODS: We reviewed our experience with 38 women who underwent chest wall resection for locally recurrent breast cancer between October 1987 and May 1997. Overall survival was calculated by the Kaplan-Meier method and the significance of prognostic variables evaluated by log-rank and Cox regression analyses. RESULTS: The operative mortality rate was 0%. Overall survival at 1, 3, and 5 years after chest wall resection was 74%, 41%, and 18%, respectively, and the proportion of patients free of local recurrence at 1, 3, and 5 years was 59%, 42%, and 13%, respectively. Regional nodal disease and size of largest tumor nodule (>4 cm) were significant predictors of local re-recurrence (P <.01, P =.04); lymph node metastasis was the only predictor of long-term survival (P <.01). Patients with and without synchronous sites of metastatic disease had near-identical 3-year survivals. CONCLUSIONS: Chest wall resection for locally recurrent breast cancer has a low mortality. However, a significant number of patients have the development of local re-recurrence or metastases, and 5-year survival is limited. It is unlikely that complete resection of all locally recurrent disease improves survival. Future studies should focus on the quality of palliation achieved.

Adult↗

PubMed1996

Cold requirement for maximal activity of the bacterial ice nucleation protein INAZ in transgenic plants.

The bacterial ice nucleation gene inaZ confers production of ice nuclei when transferred into transgenic plants. Conditioning of the transformed plant tissue at temperatures near 0 degrees C greatly increased the ice nucleation activity in plants, and maximum ice nucleation activity was achieved only after low-temperature conditioning for about 48 h. Although the transgenic plants contain similar amounts of inaZ mRNA at both normal and low temperatures, low temperatures are required for accumulation of INAZ protein. We propose that the stability of the INAZ protein and thus ice nucleation activity in the transgenic plants is enhanced by low-temperature conditioning.

Bacterial Outer Membrane Proteins↗

PubMed1994

Nuclear transport of U1 snRNP in somatic cells: differences in signal requirement compared with Xenopus laevis oocytes.

The signal requirement for the nuclear import of U1 RNA in somatic cells from different species was investigated by microinjection of both digoxygenin-labeled wild type and mutant U1 RNA molecules and in vitro reconstituted U1 snRNPs. U1 RNA was shown to be targeted to the nucleus by a temperature-dependent process that requires the prior assembly of RNPs from the common proteins and the microinjected RNA. Competition in the cell between immunoaffinity-purified U1 snRNPs and digoxygenin-labeled U1 snRNPs reconstituted in vitro showed that the transport is saturable and should therefore be a mediated process. The transport of a karyophilic protein under the same conditions was not affected, indicating the existence of a U snRNP-specific transport pathway in somatic cells, as already seen in the Xenopus laevis oocyte system. Surprisingly, the signal requirement for nuclear transport of U1 snRNP was found to differ between oocytes and somatic cells from mouse, monkey and Xenopus, in that the m3GGpppG-cap is no longer an essential signaling component in somatic cells. However, as shown by investigation of the transport kinetics of m3GpppG- and ApppG-capped U1 snRNPs, the m3GpppG-cap accelerates the rate of U1 snRNP import significantly indicating that it has retained a signaling role for nuclear targeting of U1 snRNP in somatic cells. Moreover, our data strongly suggest that cell specific rather than species specific differences account for the differential m3G-cap requirement in nuclear import of U1 snRNPs.

Animals↗

PubMed1993

A cytoplasmically anchored nuclear protein interferes specifically with the import of nuclear proteins but not U1 snRNA.

A cytoplasmically anchored mutant SV40 T antigen, FS T antigen, was shown previously to interfere specifically with the nuclear import of a heterologous nuclear protein, adenovirus 5 fiber protein, in cultured monkey cells (Schneider, J., C. Schindewolf, K. van Zee, and E. Fanning. 1988. Cell. 54:117-125; van Zee, K., F. Appel, and E. Fanning. 1991. Mol. Cell. Biol. 11:5137-5146). In this report, we demonstrate that FS T antigen also interferes with the nuclear import of adenovirus E1A and a peptide-albumin conjugate bearing multiple copies of the T antigen nuclear localization signal, but not with the import of U1 snRNA. A kinetic analysis indicates that nuclear import of the albumin-peptide conjugate is inhibited only when high intracellular concentrations of FS T antigen are reached. After microinjection into the cytoplasm of cultured cells, purified FS T antigen protein does not accumulate at the nuclear periphery, but rather is distributed in a punctate pattern throughout the cytoplasm. These data support a model in which cytoplasmic anchoring of FS T antigen enables the mutant protein to sequester and titrate out a cellular factor which is required for nuclear protein but not U1 snRNA import.

Adenovirus E1A Proteins↗

PubMed1993

Analysis of conserved binding proteins for nuclear localization sequences.

Correct targeting of nuclear proteins is mediated by nuclear localization sequences (NLS) which permit specific binding to the nucleus and subsequent translocation across the nuclear envelope via the nuclear pore complex. It is proposed that nuclear import is facilitated by NLS-receptors which reside in the cytoplasm and at the nuclear pore. These NLS-receptors could facilitate an early step of nuclear protein import, i.e. targeting and binding of nuclear proteins at the nuclear pore. We have generated anti-idiotype antibodies against the SV40 T-antigen nuclear localization sequence that allowed us to study NLS-binding proteins in a variety of different organisms. Proteins of similar size are recognized by these antibodies in yeast, Drosophila, rat and human cells. Cytological analysis indicates that the NLS-binding proteins reside in part at nuclear pores. One of the proteins recognized by anti-idiotype antibodies is identical to a previously identified NLS-binding protein. Using isolated yeast nuclei we demonstrate that the anti-idiotype antibodies compete for binding of nuclear proteins in vitro. We show that the yeast mutant npl3, which is defective in nuclear protein localization, has an altered distribution of antigens recognized by these anti-idiotype antibodies, at the semi-permissive temperature. Our results suggest that a set of proteins common to various eukaryotes recognizes nuclear localization sequences.

Amino Acid Sequence↗

PubMed1992

Asymmetric mitotic segregation of the yeast spindle pole body.

The yeast KAR1 gene is required for spindle pole body (SPB) duplication and nuclear fusion. We determine here that KAR1-beta-galactosidase hybrid proteins localize to the outer face of the SPB. Remarkably, after SPB duplication, the hybrid protein was found associated with only one of the two SPBs, usually the one that enters the bud. Using an ndc1 mutant, which forms a defective SPB at the nonpermissive temperature, we found that the hybrid was exclusively associated with the "new" SPB. Two regions of KAR1 contribute to its localization; an internal 70 residue region was necessary and sufficient to localize hybrids to the SPB, and the hydrophobic carboxyl terminus localized proteins to the nuclear envelope. The localization domains correspond to two functional domains required for SPB duplication. We suggest that KAR1 is anchored to the nuclear envelope and interacts with at least one other SPB component during the cell cycle.

Cell Compartmentation↗

PubMed1992

Intramolecular masking of the nuclear location signal and dimerization domain in the precursor for the p50 NF-kappa B subunit.

We show that the non-DNA-binding precursor for the p50 subunit (p110), like NF-kappa B, is subject to control of nuclear uptake. In contrast to p50, p110 was excluded from nuclei and unable to associate detectably with p50 or p65 NF-kappa B subunits. The nuclear location signal in the N-terminal half of p110 was not accessible for monospecific antibodies. Removal of only 191 amino acids from the C-terminus of p110 restored antibody accessibility as well as nuclear uptake. The C-terminal half of p110, which is linked to the p50 portion via a glycine-rich hinge, could also noncovalently bind to p50. This helps to explain why p50, after cleavage of the precursor in intact cells, was still retained in an inactive form in the cytoplasm. Our study describes a novel mechanism of nuclear uptake control by masking of a nuclear location signal through a remote domain within a precursor molecule.

Amino Acid Sequence↗

PubMed1992

Intracistronic complementation reveals a new function of SV40 T antigen that co-operates with Rb and p53 binding to stimulate DNA synthesis in quiescent cells.

The ability of the oncogene products of DNA tumor viruses to induce DNA synthesis in quiescent cells is thought to depend on their capacity to bind to cellular proteins such as the retinoblastoma-suppressor protein Rb and the tumor suppressor p53, thereby abolishing the growth-arresting properties of these proteins. We have tested this hypothesis using SV40 T antigens carrying lesions that affect Rb binding, p53 binding or other functions involved in cell transformation. The results demonstrate that Rb binding is not essential for growth stimulation by T antigen. However, detailed analysis, including intracistronic complementation, suggests that at least three functions, Rb binding, a novel second activity localized to the DNA-binding domain and a function residing in the carboxy terminus, probably p53 binding, cooperate to generate the full growth induction potential of T antigen.

Animals↗

PubMed1991

A hydrophobic protein sequence can override a nuclear localization signal independently of protein context.

Simian virus 40 T antigen is specifically targeted to the nucleus by the signal Pro-Lys-Lys-128-Lys-Arg-Lys-Val. We have previously described the isolation of a simian virus 40 T-antigen mutant, 676FS, which retains a wild-type nuclear localization signal but fails to accumulate properly in the nucleus and interferes with the nuclear localization of heterologous proteins. Here we report that the hydrophobic carboxy-terminal sequence novel to 676FS T antigen overrides the nuclear localization signal if fused to other proteins, thereby anchoring the proteins in the cytoplasm. We discuss possible mechanisms by which missorting of such a fusion protein could interfere with the nuclear transport of heterologous proteins.

Amino Acid Sequence↗

PubMed1988

A mutant SV40 large T antigen interferes with nuclear localization of a heterologous protein.

A mutant SV40 genome carrying a frameshift at the carboxyl terminus of the large T antigen failed to replicate SV40 DNA and to transform rat2 cells, although the altered region is known to be dispensable for these functions. The mutant T antigen also failed to localize normally in the nucleus and interfered with nuclear localization of at least one other nuclear protein, adenovirus fiber. A double mutant carrying an additional lesion in the nuclear localization signal was also localized in the cytoplasm, but regained the ability to transform rat2 cells and no longer affected the nuclear localization of fiber protein. We suggest that the frameshift T antigen may disrupt a mechanism required for nuclear localization of proteins.

Adenoviruses, Human↗