Biomedical subjects

Nancy Olashaw

Publications and source records attributed to Nancy Olashaw.

6 recordsLinked to original sources

PubMed2004

ERK couples chronic survival of NK cells to constitutively activated Ras in lymphoproliferative disease of granular lymphocytes (LDGL).

Chronic NK lymphoproliferative disease of large granular lymphocytes (LDGL) is characterized by the expansion of activated CD3-, CD16+ or CD56+ lymphocytes. The mechanism of survival of NK cells from LDGL patients is unknown but may be related to antigenic stimulation. There is currently no standard effective therapy for LDGL, and the disease is characteristically resistant to standard forms of chemotherapy. We found evidence of constitutive activation of extracellular-regulated kinase (ERK) in NK cells from 13/13 patients with NK-LDGL (one patient with aggressive and 12 patients with chronic disease). Ablation of ERK activity by inhibitors or a dominant-negative form of MEK, the upstream activator of ERK, reduced the survival of patient NK cells. Ras was also constitutively active in patient NK cells, and exposure of cells to the Ras inhibitor FTI2153 or to dominant-negative-Ras resulted not only in ERK inhibition but also in enhanced apoptosis in both the presence and absence of anti-Fas. Therefore, we conclude that a constitutively active Ras/MEK/ERK pathway contributes to the accumulation of NK cells in patients with NK-LDGL. These findings suggest that strategies to inhibit this signaling pathway may be useful for the treatment of the NK type of LDGL.

Blotting, Western↗

PubMed2004

Molecular cloning and functional characterization of the transcription factor YY2.

YY1 is a ubiquitous zinc finger transcription factor that binds to and regulates promoters and enhancers of many cellular and viral genes. Here we report the isolation of a human cDNA encoding a DNA sequence-specific binding protein with significant homology to the transcription factor YY1. A sequence analysis of this novel protein, YY2, revealed an overall 65% identity in the DNA sequence and a 56% identity in protein sequence compared with human YY1. The most pronounced similarity between YY1 and YY2 exists within the zinc finger regions of the two proteins, and consistent with this observation, YY2 can bind to and regulate some promoters known to be controlled by YY1. Similar to YY1, YY2 contains both transcriptional activation and repression functions. The finding of a protein with structure and function similar to YY1 provides a new opportunity to explore additional mechanisms by which YY1-responsive genes can be regulated and suggests that gene regulation by YY1 is far more complicated than previously assumed.

Amino Acid Sequence↗

PubMed2004

Cell cycle control: a complex issue.

Do p27Kip1 and p21Cip1 function as activators or inhibitors of D cyclin-cdk4 activity? Attempts to answer this question, and thus to understand how cdk4--a key cell cycle regulator--becomes active, have produced conflicting data. In this perspective, we summarize the results of studies addressing the effects of p27Kip1 and p21Cip1 on the assembly and activation of D cyclin-cdk4 complexes. Emphasis is placed on our experimental findings that support a model of cell cycle control in which p27Kip1 and p21Cip1 stabilize D cyclin-cdk4 complexes but inhibit D cyclin-cdk4 activity.

Animals↗

PubMed2004

Activation of the growth-differentiation factor 11 gene by the histone deacetylase (HDAC) inhibitor trichostatin A and repression by HDAC3.

Histone deacetylase (HDAC) inhibitors inhibit the proliferation of transformed cells in vitro, restrain tumor growth in animals, and are currently being actively exploited as potential anticancer agents. To identify gene targets of the HDAC inhibitor trichostatin A (TSA), we compared the gene expression profiles of BALB/c-3T3 cells treated with or without TSA. Our results show that TSA up-regulates the expression of the gene encoding growth-differentiation factor 11 (Gdf11), a transforming growth factor beta family member that inhibits cell proliferation. Detailed analyses indicated that TSA activates the gdf11 promoter through a conserved CCAAT box element. A comprehensive survey of human HDACs revealed that HDAC3 is necessary and sufficient for the repression of gdf11 promoter activity. Chromatin immunoprecipitation assays showed that treatment of cells with TSA or silencing of HDAC3 expression by small interfering RNA causes the hyperacetylation of Lys-9 in histone H3 on the gdf11 promoter. Together, our results provide a new model in which HDAC inhibitors reverse abnormal cell growth by inactivation of HDAC3, which in turn leads to the derepression of gdf11 expression.

Acetylation↗

PubMed2004

AG490 inhibits G1-S traverse in BALB/c-3T3 cells following either mitogenic stimulation or exogenous expression of E2F-1.

AG490, a member of the tryphostin family of protein kinase inhibitors, repressed G(0)-G(1) traverse in BALB/c-3T3 cells. While the early induction of STAT activity was repressed by AG490, extracellular signal-regulated kinase (ERK) activation was unaffected and a pattern of gene expression suggested that cells exited G(0) in the presence of the inhibitor. Although AG490 did not alter the induction of cyclin D1 protein, neither cyclin D1- nor cyclin D3-associated kinase activity was observed in growth-inhibited cells. Surprisingly, p130 was partially phosphorylated, and E2F3A protein was expressed in mitogen-stimulated AG490-treated cells despite the lack of cyclin D-associated kinase activity. These data suggest that AG490 inhibits a cellular pathway required for mid-G(0)-G(1) traverse that is located after the induction of early processes potentially mediated by E2F (although independent of cyclin D-associated kinase activity) but before the late G(1) increase in E2F-dependent transcription. Infection of AG490-treated cells with an E2F-1 adenovirus caused the induction of cyclin A, but could not overcome the drug-induced cell cycle arrest that was coincident with the repression of cyclin-dependent kinase 2 (cdk2)-associated kinase activation. We conclude that cdk2-associated kinase activity is modulated by a cellular process repressed by AG490. Furthermore, this cdk2-associated kinase activity is required for G(0)-G(1) traverse in some role other than the regulation of E2F-dependent transcription.

Animals↗

PubMed2002

Paradigms of growth control: relation to Cdk activation.

The cyclin-dependent kinases (CDKs) play a key role in cell cycle control, and in this review, we focus on the events that regulate their activities. Emphasis is placed on the CDKs that function during the G(1) phase of the cell cycle and on the CDK inhibitor p27(Kip1). We discuss how CDK activation relates to two basic concepts of cell cycle regulation: (i) the need for multiple mitogens for the proliferation of nontransformed cells and (ii) the inhibitory effect of high culture density on proliferative capacity. We also describe how Cdk2 modulates the expression of the alpha subunit of the interleukin-2 receptor in T cells, and address the question of whether p27(Kip1) functions as an activator or inhibitor of the CDKs associated with the D cyclins.

Animals↗