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C Featherstone

Publications and source records attributed to C Featherstone.

47 records · Page 3Linked to original sources
PubMed1991

p55CDC25 is a nuclear protein required for the initiation of mitosis in human cells.

The cdc25+ gene of fission yeast encodes a phosphotyrosine phosphatase that dephosphorylates tyrosine-15 of p34cdc2 and thereby activates p34cdc2/cyclin to bring about entry into M phase. We have recently cloned a human homolog, CDC25, which rescues the M-phase initiation defect of yeast cdc25 temperature-sensitive mutants. Antibodies raised against the CDC25 gene product specifically recognize human proteins of approximately 55 and approximately 52 kDa. Microinjection of affinity-purified anti-CDC25 antibodies into HeLa cells inhibits entry into mitosis. These observations suggest that the CDC25 gene products are essential for the initiation of mitosis in human cells, similar to their homologs in fission yeast and Drosophila. CDC25 gene products, like p34CDC2, are localized primarily in the nucleus during interphase, suggesting that activation of p34CDC2/cyclin by p52/p55CDC25 occurs within the nucleus.

Cell Cycle↗
PubMed1991

Fission yeast p107wee1 mitotic inhibitor is a tyrosine/serine kinase.

The fission yeast wee1+ gene product is a dose-dependent, negative regulator of entry into mitosis. wee1+ encodes a protein of relative molecular mass 107,000 (Mr 107K), the C-terminal third of which has strong similarities with the serine/threonine protein kinase family. Here we report that p107wee1 immune complexes phosphorylate p107wee1 equally on serine and tyrosine residues, and also phosphorylate an exogenous substrate, angiotensin II, on tyrosine. Both kinase activities are attributable to p107wee1 because they are also observed when wee1+ is expressed in heterologous systems; both are abolished by a point mutation in the ATP-binding domain, and both behave like an asymmetric monomer of Mr114K on gel filtration and density-gradient centrifugation. Thus the wee1+ gene product is representative of a novel class of protein kinase that phosphorylates both serine and tyrosine residues.

Animals↗
PubMed1988

A monoclonal antibody against the nuclear pore complex inhibits nucleocytoplasmic transport of protein and RNA in vivo.

A monoclonal antibody that reacts with proteins in the nuclear pore complex of rat liver (Snow, C. M., A. Senior, and L. Gerace. 1987. J. Cell Biol. 104:1143-1156) has been shown to cross react with similar components in Xenopus oocytes, as determined by immunofluorescence microscopy and immunoblotting. We have microinjected the antibody into oocytes to study the possible role of these polypeptides in nucleocytoplasmic transport. The antibody inhibits import of a large nuclear protein, nucleoplasmin, in a time- and concentration-dependent manner. It also inhibits export of 5S ribosomal RNA and mature tRNA, but has no effect on transcription or intranuclear tRNA processing. The antibody does not affect the rate of diffusion into the nucleus of two small proteins, myoglobin and ovalbumin, indicating that antibody binding does not result in occlusion of the channel for diffusion. This suggests that inhibition of protein and RNA transport occurs by binding of the antibody at or near components of the pore that participate in mediated transport.

Animals↗
PubMed1985

Newly synthesized G protein of vesicular stomatitis virus is not transported to the Golgi complex in mitotic cells.

Newly synthesized G protein of vesicular stomatitis virus is not transported to the surface of cultured mammalian cells during mitosis (Warren et al., 1983, J. Cell Biol. 97:1623-1628). To determine where intracellular transport is inhibited, we have examined the post-translational modifications of G protein, which are indicators of specific compartments on the transport pathway. G protein in mitotic cells had only endo H-sensitive oligosaccharides containing seven or eight mannose residues, but no terminal glucose, and was not fatty acylated. These modifications were indicative of processing only by enzymes of the endoplasmic reticulum (ER). Quantitative immunocytochemistry was used as an independent method to confirm that transport of G protein out of the ER was inhibited. The density of G protein in the ER cisternae was 2.5 times greater than in infected G1 cells treated similarly. Incubation of infected mitotic cells with cycloheximide, which inhibits protein synthesis without affecting transport, did not result in a decrease in the density of G protein in the ER cisternae, demonstrating that G protein cannot be chased out of the ER. These results suggest that intracellular transport stops at or before the first vesicle-mediated step on the pathway.

Animals↗
PubMed1983

Newly synthesized G protein of vesicular stomatitis virus is not transported to the cell surface during mitosis.

Indirect immunofluorescence, immunoelectron microscopy, and digestion by protease were used to study intracellular transport of the G protein of vesicular stomatitis virus in mitotic and interphase cells. Quantitation showed that the appearance of G protein on the surface of mitotic cells was inhibited at least 10-fold when compared with that on interphase cells, even though similar amounts of viral protein were being synthesized. This dramatic inhibition, taken together with the simultaneous inhibition of endocytosis (Berlin, R. D., and J. M. Oliver, 1980, J. Cell Biol. 85: 660-671), points to a general cessation of membrane traffic in the mitotic cell.

Animals↗