S49 lymphoma tissue culture cells arrest in the G1 phase of the cell cycle when treated with agen... more S49 lymphoma tissue culture cells arrest in the G1 phase of the cell cycle when treated with agents that elevate endogenous cyclic adenosine 3':5'-monophosphate (cAMP), such as cholera toxin or exogenously added active congeners of cAMP such as N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP). This phenomenon requires that cells contain the appropriate receptors: Mutant cells deficient in adenylyl cyclase fail to arrest in response to cholera toxin, and another mutant that lacks cAMP-dependent protein kinase does not respond to cholera toxin or to Bt2cAMP. The size distribution of cell populations treated with Bt2cAMP changes in a manner that reflects only the perturbation of cell cycle distribution. Arrested G1 cells in particular have the same volume as the G1 cells of an exponentially growing population. When G1 cells that have been arrested by Bt2cAMP are grown in fresh medium free of Bt2cAMP, they begin to reenter S phase after a delay of abou...
Dibutyryl cyclic adenosine 3',5'-monophosphate (cyclic AMP) produces phosphodiest... more Dibutyryl cyclic adenosine 3',5'-monophosphate (cyclic AMP) produces phosphodiesterase induction, growth arrest, and cytolysis in S49 lymphoma cells. The striking parallelism between protein kinase activity that is dependent on cytosol cyclic AMP and cellular responses to dibutyryl cyclic AMP in wild-type cells and three classes of clones resistant to cyclic AMP indicates that protein kinase mediates cyclic AMP regulation of growth and enzyme induction in S49 cells.
The mechanism of protein quality control and elimination of misfolded proteins in the cytoplasm i... more The mechanism of protein quality control and elimination of misfolded proteins in the cytoplasm is poorly understood. We studied the involvement of cytoplasmic factors required for degradation of two endoplasmic reticulum (ER)-import-defective mutated derivatives of carboxypeptidase yscY (DeltassCPY* and DeltassCPY*-GFP) and also examined the requirements for degradation of the corresponding wild-type enzyme made ER-import incompetent by removal of its signal sequence (DeltassCPY). All these protein species are rapidly degraded via the ubiquitin-proteasome system. Degradation requires the ubiquitin-conjugating enzymes Ubc4p and Ubc5p, the cytoplasmic Hsp70 Ssa chaperone machinery, and the Hsp70 cochaperone Ydj1p. Neither the Hsp90 chaperones nor Hsp104 or the small heat-shock proteins Hsp26 and Hsp42 are involved in the degradation process. Elimination of a GFP fusion (GFP-cODC), containing the C-terminal 37 amino acids of ornithine decarboxylase (cODC) directing this enzyme to the ...
The antizymes constitute a conserved gene family with at least three mammalian orthologs. As desc... more The antizymes constitute a conserved gene family with at least three mammalian orthologs. As described previ- ously, in a degradation system utilizing rabbit reticulo- cyte lysate, antizyme 1 (AZ1) accelerates proteasomal or- nithine decarboxylase (ODC) degradation, but antizyme 2 (AZ2) does not. To examine the relationship between an- tizyme structure and function, we further characterized the properties of AZ1 and
Proceedings of The National Academy of Sciences, 1977
We have previously selected and characterized mutant S49 mouse lymphoma cells that possess an ade... more We have previously selected and characterized mutant S49 mouse lymphoma cells that possess an adenosine 3':5'-cyclic monophosphate (cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) with an increased apparent affinity constant (Ka) for activation by cAMP. The Ka lesion in one such mutant clone has been shown to result from a structural mutation involving the kinase holoenzyme's regulatory (R) subunit. The
Crystals of truncated (delta425-461) pyridoxal-5'-phosphate (PLP)-dependent mouse... more Crystals of truncated (delta425-461) pyridoxal-5'-phosphate (PLP)-dependent mouse ornithine decarboxylase (mOrnDC') have been obtained that diffract to 2.2 angstroms resolution (P2(1)2(1)2, a = 119.5 angstroms, b = 74.3 angstroms, c = 46.1 angstroms). OrnDC produces putrescine, which is the precursor for the synthesis of polyamines in eukaryotes. Regulation of activity and understanding of the mechanism of action of this enzyme may aid in the development of compounds against cancer. mOrnDC is a member of group IV PLP-dependent decarboxylases, for which there are no known representative structures.
Proceedings of the National Academy of Sciences, 1975
Flow-microfluorimetric analysis has been carried out on populations of exponentially growing S49 ... more Flow-microfluorimetric analysis has been carried out on populations of exponentially growing S49 mouse lymphoma cells treated with dibutyryl cyclic AMP. The drug produces a specific concentration-dependent block in the G-1 phase of the cell cycle while other phases of the cycle are not perceptibly altered. The cell cycle of a line of mutant cells lacking the cyclic AMP-dependent protein kinase is not affected by the drug. Since these mutant cells have been shown to maintain a normal cell cycle, even in the presence of high levels of cyclic AMP, periodic fluctuations in the levels of the cyclic nucleotide cannot be required for or determine progression through the cell cycle.
Proceedings of the National Academy of Sciences, 1975
Compared to the wild-type parental line of S49 mouse lymphoma cells, intact cells of a mutant lin... more Compared to the wild-type parental line of S49 mouse lymphoma cells, intact cells of a mutant line (kin.A) are 10-fold less sensititive to biologic effects of exogenous cyclic adenosine 3':5'-monophophosphate (cAMP), such as induction of cAMP phosphodiesterase, cell cycle-specific growth inhibition, and cytolysis. The cAMP-dependent protein kinase (ATP:protein phosphotransferase; EC 2.7.1.37) activity of kin.A cells exhibits an apparent Ka for activation by cAMP 10-fold greater than that of wild type, and is much more resistant to inactivation by heat. These differences between the wild-type and mutant enzymes persist through a high degree of purification, suggesting a structural alteration in the kin.A holoenzyme. Heterologous reconstitution experiments, using separated R and C subunits of the wild-type and kin.A cAMP-dependent kinases, show that the altered cAMP affinity and thermolability are conferred by the R component of the kin.A enzyme. These results are most consistent with a structural mutation in the kin.A gene coding for the R subunit of cAMP-dependent protein kinase. Evidence for a structural mutation helps to define one mechanism of heritable variation in cultured somatic cells. The phenotype produced by the kin.A structural mutation also greatly strengthens the conslusion that cAMP-dependent protein kinase is essential for cAMP regulation of growth and enzyme induction in intact S49 cells.
S49 mouse lymphoma cell mutants, each with a specific defect in its ability to generate or respon... more S49 mouse lymphoma cell mutants, each with a specific defect in its ability to generate or respond to cyclic AMP, have been isolated. Analysis of the properties of these cells has begun to provide information on complex and significant biologic problems related to the cyclic AMP system.
S49 lymphoma tissue culture cells arrest in the G1 phase of the cell cycle when treated with agen... more S49 lymphoma tissue culture cells arrest in the G1 phase of the cell cycle when treated with agents that elevate endogenous cyclic adenosine 3':5'-monophosphate (cAMP), such as cholera toxin or exogenously added active congeners of cAMP such as N6,O2'-dibutyryl cyclic adenosine 3':5'-monophosphate (Bt2cAMP). This phenomenon requires that cells contain the appropriate receptors: Mutant cells deficient in adenylyl cyclase fail to arrest in response to cholera toxin, and another mutant that lacks cAMP-dependent protein kinase does not respond to cholera toxin or to Bt2cAMP. The size distribution of cell populations treated with Bt2cAMP changes in a manner that reflects only the perturbation of cell cycle distribution. Arrested G1 cells in particular have the same volume as the G1 cells of an exponentially growing population. When G1 cells that have been arrested by Bt2cAMP are grown in fresh medium free of Bt2cAMP, they begin to reenter S phase after a delay of abou...
Dibutyryl cyclic adenosine 3',5'-monophosphate (cyclic AMP) produces phosphodiest... more Dibutyryl cyclic adenosine 3',5'-monophosphate (cyclic AMP) produces phosphodiesterase induction, growth arrest, and cytolysis in S49 lymphoma cells. The striking parallelism between protein kinase activity that is dependent on cytosol cyclic AMP and cellular responses to dibutyryl cyclic AMP in wild-type cells and three classes of clones resistant to cyclic AMP indicates that protein kinase mediates cyclic AMP regulation of growth and enzyme induction in S49 cells.
The mechanism of protein quality control and elimination of misfolded proteins in the cytoplasm i... more The mechanism of protein quality control and elimination of misfolded proteins in the cytoplasm is poorly understood. We studied the involvement of cytoplasmic factors required for degradation of two endoplasmic reticulum (ER)-import-defective mutated derivatives of carboxypeptidase yscY (DeltassCPY* and DeltassCPY*-GFP) and also examined the requirements for degradation of the corresponding wild-type enzyme made ER-import incompetent by removal of its signal sequence (DeltassCPY). All these protein species are rapidly degraded via the ubiquitin-proteasome system. Degradation requires the ubiquitin-conjugating enzymes Ubc4p and Ubc5p, the cytoplasmic Hsp70 Ssa chaperone machinery, and the Hsp70 cochaperone Ydj1p. Neither the Hsp90 chaperones nor Hsp104 or the small heat-shock proteins Hsp26 and Hsp42 are involved in the degradation process. Elimination of a GFP fusion (GFP-cODC), containing the C-terminal 37 amino acids of ornithine decarboxylase (cODC) directing this enzyme to the ...
The antizymes constitute a conserved gene family with at least three mammalian orthologs. As desc... more The antizymes constitute a conserved gene family with at least three mammalian orthologs. As described previ- ously, in a degradation system utilizing rabbit reticulo- cyte lysate, antizyme 1 (AZ1) accelerates proteasomal or- nithine decarboxylase (ODC) degradation, but antizyme 2 (AZ2) does not. To examine the relationship between an- tizyme structure and function, we further characterized the properties of AZ1 and
Proceedings of The National Academy of Sciences, 1977
We have previously selected and characterized mutant S49 mouse lymphoma cells that possess an ade... more We have previously selected and characterized mutant S49 mouse lymphoma cells that possess an adenosine 3':5'-cyclic monophosphate (cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) with an increased apparent affinity constant (Ka) for activation by cAMP. The Ka lesion in one such mutant clone has been shown to result from a structural mutation involving the kinase holoenzyme's regulatory (R) subunit. The
Crystals of truncated (delta425-461) pyridoxal-5'-phosphate (PLP)-dependent mouse... more Crystals of truncated (delta425-461) pyridoxal-5'-phosphate (PLP)-dependent mouse ornithine decarboxylase (mOrnDC') have been obtained that diffract to 2.2 angstroms resolution (P2(1)2(1)2, a = 119.5 angstroms, b = 74.3 angstroms, c = 46.1 angstroms). OrnDC produces putrescine, which is the precursor for the synthesis of polyamines in eukaryotes. Regulation of activity and understanding of the mechanism of action of this enzyme may aid in the development of compounds against cancer. mOrnDC is a member of group IV PLP-dependent decarboxylases, for which there are no known representative structures.
Proceedings of the National Academy of Sciences, 1975
Flow-microfluorimetric analysis has been carried out on populations of exponentially growing S49 ... more Flow-microfluorimetric analysis has been carried out on populations of exponentially growing S49 mouse lymphoma cells treated with dibutyryl cyclic AMP. The drug produces a specific concentration-dependent block in the G-1 phase of the cell cycle while other phases of the cycle are not perceptibly altered. The cell cycle of a line of mutant cells lacking the cyclic AMP-dependent protein kinase is not affected by the drug. Since these mutant cells have been shown to maintain a normal cell cycle, even in the presence of high levels of cyclic AMP, periodic fluctuations in the levels of the cyclic nucleotide cannot be required for or determine progression through the cell cycle.
Proceedings of the National Academy of Sciences, 1975
Compared to the wild-type parental line of S49 mouse lymphoma cells, intact cells of a mutant lin... more Compared to the wild-type parental line of S49 mouse lymphoma cells, intact cells of a mutant line (kin.A) are 10-fold less sensititive to biologic effects of exogenous cyclic adenosine 3':5'-monophophosphate (cAMP), such as induction of cAMP phosphodiesterase, cell cycle-specific growth inhibition, and cytolysis. The cAMP-dependent protein kinase (ATP:protein phosphotransferase; EC 2.7.1.37) activity of kin.A cells exhibits an apparent Ka for activation by cAMP 10-fold greater than that of wild type, and is much more resistant to inactivation by heat. These differences between the wild-type and mutant enzymes persist through a high degree of purification, suggesting a structural alteration in the kin.A holoenzyme. Heterologous reconstitution experiments, using separated R and C subunits of the wild-type and kin.A cAMP-dependent kinases, show that the altered cAMP affinity and thermolability are conferred by the R component of the kin.A enzyme. These results are most consistent with a structural mutation in the kin.A gene coding for the R subunit of cAMP-dependent protein kinase. Evidence for a structural mutation helps to define one mechanism of heritable variation in cultured somatic cells. The phenotype produced by the kin.A structural mutation also greatly strengthens the conslusion that cAMP-dependent protein kinase is essential for cAMP regulation of growth and enzyme induction in intact S49 cells.
S49 mouse lymphoma cell mutants, each with a specific defect in its ability to generate or respon... more S49 mouse lymphoma cell mutants, each with a specific defect in its ability to generate or respond to cyclic AMP, have been isolated. Analysis of the properties of these cells has begun to provide information on complex and significant biologic problems related to the cyclic AMP system.
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Papers by Philip Coffino