y yan - Profile on Academia.edu (original) (raw)

Papers by y yan

Research paper thumbnail of Inhibition of Protein Phosphatase Activity Induces p53-dependent Apoptosis in the Absence of p53 Transactivation

Journal of Biological Chemistry, 1997

Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of pro... more Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of protein phosphorylation in regulating the functions of endogenous p53. Exposure of Balb/c 3T3 cells to okadaic acid, an inhibitor of protein phosphatases 1 and 2A, increased the phosphorylation of p53 without changing p53 levels. Okadaic acid treatment enhanced the binding of p53 to a consensus DNA target sequence and caused a 5-8-fold increase in p53 transcriptional activity. Transient expression of SV40 small tumor antigen, a specific inhibitor of protein phosphatase 2A, caused a 4-fold increase in p53 transcriptional activity. Incubation of Balb/c 3T3 cells with okadaic acid also induced programmed cell death in a dose-and time-dependent manner. Decreases in viability, morphological changes, and the appearance of DNA fragmentation were dependent on p53 since cells lacking functional p53 were resistant to okadaic acidinduced apoptosis. The p53-dependent apoptosis induced by okadaic acid was rapid and did not require p53 transcriptional activity. The fact that SV40 small tumor antigen did not induce apoptosis provides additional evidence that p53 transcriptional activity is not sufficient for p53-mediated apoptosis. These results indicate that signaling pathways involving protein phosphorylation play critical roles in controlling the apoptotic activity of p53. Furthermore, a basal level of protein phosphatase 1 or 2A activity is necessary to prevent p53dependent apoptosis.

Research paper thumbnail of Inhibition of Protein Phosphatase Activity Induces p53-dependent Apoptosis in the Absence of p53 Transactivation

Journal of Biological Chemistry, 1997

Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of pro... more Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of protein phosphorylation in regulating the functions of endogenous p53. Exposure of Balb/c 3T3 cells to okadaic acid, an inhibitor of protein phosphatases 1 and 2A, increased the phosphorylation of p53 without changing p53 levels. Okadaic acid treatment enhanced the binding of p53 to a consensus DNA target sequence and caused a 5-8-fold increase in p53 transcriptional activity. Transient expression of SV40 small tumor antigen, a specific inhibitor of protein phosphatase 2A, caused a 4-fold increase in p53 transcriptional activity. Incubation of Balb/c 3T3 cells with okadaic acid also induced programmed cell death in a dose-and time-dependent manner. Decreases in viability, morphological changes, and the appearance of DNA fragmentation were dependent on p53 since cells lacking functional p53 were resistant to okadaic acidinduced apoptosis. The p53-dependent apoptosis induced by okadaic acid was rapid and did not require p53 transcriptional activity. The fact that SV40 small tumor antigen did not induce apoptosis provides additional evidence that p53 transcriptional activity is not sufficient for p53-mediated apoptosis. These results indicate that signaling pathways involving protein phosphorylation play critical roles in controlling the apoptotic activity of p53. Furthermore, a basal level of protein phosphatase 1 or 2A activity is necessary to prevent p53dependent apoptosis.

Research paper thumbnail of Mass flow measurement of bulk solids in pneumatic pipelines

Many types of techniques for metering the mass flow rate of bulk solids in a pneumatic pipeline h... more Many types of techniques for metering the mass flow rate of bulk solids in a pneumatic pipeline have been proposed and developed during the past 20 years. This paper presents a detailed and comprehensive review of the techniques and the current state of knowledge and experience. The techniques are classified under three main categories: direct measurement of solids mass flow rates, measurement of volumetric concentrations of solids and measurement of solids velocity. Future developments and possible trends in this field are also included.

Research paper thumbnail of Crystal Structure of the Repetitive Segments of Spectrin

Crystal Structure of the Repetitive Segments of Spectrin

Science, 1993

The elongated proteins of the spectrin family (dystrophin, alpha-actinin, and spectrin) contain t... more The elongated proteins of the spectrin family (dystrophin, alpha-actinin, and spectrin) contain tandemly repeated segments and form resilient cellular meshworks by cross-linking actin filaments. The structure of one of the repetitive segments of alpha-spectrin was determined at a 1.8 angstrom resolution. A segment consists of a three-helix bundle. A model of the interface between two tandem segments suggests that hydrophobic interactions between segments may constrain intersegment flexibility. The helix side chain interactions explain how mutations that are known to produce hemolytic anemias disrupt spectrin associations that sustain the integrity of the erythrocyte membrane.

Research paper thumbnail of Structure of simian virus 40 at 3.8-Å resolution

Structure of simian virus 40 at 3.8-Å resolution

Nature, 1991

The crystallographically determined structure of simian virus 40 shows that the 72 pentamers of v... more The crystallographically determined structure of simian virus 40 shows that the 72 pentamers of viral protein VP1, which form the outer shell, have identical conformations except for the C-terminal arms of their subunits. Five arms emerge from each pentamer and insert into neighbouring pentamers. This tying together of standard building blocks allows for the required variability in packing geometry without sacrificing specificity.

Research paper thumbnail of Inhibition of Protein Phosphatase Activity Induces p53-dependent Apoptosis in the Absence of p53 Transactivation

Journal of Biological Chemistry, 1997

Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of pro... more Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of protein phosphorylation in regulating the functions of endogenous p53. Exposure of Balb/c 3T3 cells to okadaic acid, an inhibitor of protein phosphatases 1 and 2A, increased the phosphorylation of p53 without changing p53 levels. Okadaic acid treatment enhanced the binding of p53 to a consensus DNA target sequence and caused a 5-8-fold increase in p53 transcriptional activity. Transient expression of SV40 small tumor antigen, a specific inhibitor of protein phosphatase 2A, caused a 4-fold increase in p53 transcriptional activity. Incubation of Balb/c 3T3 cells with okadaic acid also induced programmed cell death in a dose-and time-dependent manner. Decreases in viability, morphological changes, and the appearance of DNA fragmentation were dependent on p53 since cells lacking functional p53 were resistant to okadaic acidinduced apoptosis. The p53-dependent apoptosis induced by okadaic acid was rapid and did not require p53 transcriptional activity. The fact that SV40 small tumor antigen did not induce apoptosis provides additional evidence that p53 transcriptional activity is not sufficient for p53-mediated apoptosis. These results indicate that signaling pathways involving protein phosphorylation play critical roles in controlling the apoptotic activity of p53. Furthermore, a basal level of protein phosphatase 1 or 2A activity is necessary to prevent p53dependent apoptosis.

Research paper thumbnail of Inhibition of Protein Phosphatase Activity Induces p53-dependent Apoptosis in the Absence of p53 Transactivation

Journal of Biological Chemistry, 1997

Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of pro... more Inhibitors of type 1 and type 2A protein phosphatases were used to examine the involvement of protein phosphorylation in regulating the functions of endogenous p53. Exposure of Balb/c 3T3 cells to okadaic acid, an inhibitor of protein phosphatases 1 and 2A, increased the phosphorylation of p53 without changing p53 levels. Okadaic acid treatment enhanced the binding of p53 to a consensus DNA target sequence and caused a 5-8-fold increase in p53 transcriptional activity. Transient expression of SV40 small tumor antigen, a specific inhibitor of protein phosphatase 2A, caused a 4-fold increase in p53 transcriptional activity. Incubation of Balb/c 3T3 cells with okadaic acid also induced programmed cell death in a dose-and time-dependent manner. Decreases in viability, morphological changes, and the appearance of DNA fragmentation were dependent on p53 since cells lacking functional p53 were resistant to okadaic acidinduced apoptosis. The p53-dependent apoptosis induced by okadaic acid was rapid and did not require p53 transcriptional activity. The fact that SV40 small tumor antigen did not induce apoptosis provides additional evidence that p53 transcriptional activity is not sufficient for p53-mediated apoptosis. These results indicate that signaling pathways involving protein phosphorylation play critical roles in controlling the apoptotic activity of p53. Furthermore, a basal level of protein phosphatase 1 or 2A activity is necessary to prevent p53dependent apoptosis.

Research paper thumbnail of Mass flow measurement of bulk solids in pneumatic pipelines

Many types of techniques for metering the mass flow rate of bulk solids in a pneumatic pipeline h... more Many types of techniques for metering the mass flow rate of bulk solids in a pneumatic pipeline have been proposed and developed during the past 20 years. This paper presents a detailed and comprehensive review of the techniques and the current state of knowledge and experience. The techniques are classified under three main categories: direct measurement of solids mass flow rates, measurement of volumetric concentrations of solids and measurement of solids velocity. Future developments and possible trends in this field are also included.

Research paper thumbnail of Crystal Structure of the Repetitive Segments of Spectrin

Crystal Structure of the Repetitive Segments of Spectrin

Science, 1993

The elongated proteins of the spectrin family (dystrophin, alpha-actinin, and spectrin) contain t... more The elongated proteins of the spectrin family (dystrophin, alpha-actinin, and spectrin) contain tandemly repeated segments and form resilient cellular meshworks by cross-linking actin filaments. The structure of one of the repetitive segments of alpha-spectrin was determined at a 1.8 angstrom resolution. A segment consists of a three-helix bundle. A model of the interface between two tandem segments suggests that hydrophobic interactions between segments may constrain intersegment flexibility. The helix side chain interactions explain how mutations that are known to produce hemolytic anemias disrupt spectrin associations that sustain the integrity of the erythrocyte membrane.

Research paper thumbnail of Structure of simian virus 40 at 3.8-Å resolution

Structure of simian virus 40 at 3.8-Å resolution

Nature, 1991

The crystallographically determined structure of simian virus 40 shows that the 72 pentamers of v... more The crystallographically determined structure of simian virus 40 shows that the 72 pentamers of viral protein VP1, which form the outer shell, have identical conformations except for the C-terminal arms of their subunits. Five arms emerge from each pentamer and insert into neighbouring pentamers. This tying together of standard building blocks allows for the required variability in packing geometry without sacrificing specificity.