11,225 research outputs found
Transcription Factor AP-2 Regulatory Signatures in Breast Cancer
No full textPhDAP-2 transcription factors are highly conserved basic helix-span-helix proteins whose
members ((x, ß, y, S and c) are crucial regulators of bryonic development. They also
play an important role in human neoplasia. uohis ochemical studies have detected
high levels of AP-2y expression in primary tumo of breast cancer patients. This high
expression has been correlated with reduced survival in all patients and reduced survival
in an ERa positive subset treated with hormone therapy. In breast cancer cell lines, AP-
2 factors have been implicated in the regulation of the ERBB2 proto-oncogene and ERa.
In an effort to further understand the role of AP-2y in breast carcinoma, this study has
sought to identify additional AP-2 activated cellular pathways and ultimately novel
transcriptional targets for AP-2 through the use of gene expression profiling.
RNAi using three independent AP-2y targeting sequences, has been used to deplete AP-
2y levels in the ERa positive MCF-7 breast carcinoma cell line, chosen as it exclusively
expresses the AP-2y family member. Microarrays were then utilised to create an AP-2y
dependent transcription profile. Statistical comparisons between non-silencing control
siRNA and AP-2y targeting siRNA groups identified a total of 162 gene expression
changes (p<0.01). These changes implicate AP-2y in the control of cell cycle
progression and developmental signalling. Indeed a role for AP-2y in the control of cell
cycle, in particular at the GUS transition, has been verified using flow cytometry.
Several of these gene expression changes, including IGFBP3, Transgelin and
KIAA1324, have been confirmed using qPCR and immunoblotting.
Finally, elevated levels of p21 mRNA and protein have been observed following AP-2y
silencing in MCF-7 cells. Additionally, the activity of a p21 promoter reporter is
repressed following transfection with an AP-2y expression construct in HepG2 cells.
These results coupled with ChIP experiments showing AP-2y occupancy at the proximal
promoter region of p21 in cycling MCF-7 cells, implicate AP-2y in the repression of
p21 transcription and suggest a role for AP2y in- the, control of cell cycle in breast
carcinoma in part through the transcriptional repression of p21
Regulation of breast tumour cell survival by AP-2 transcription factors
No full textPhDAP-2 transcription factors are crucial regulators of embryonic development and also
play important roles in human neoplasia. Over-expression of AP-2α and AP-2γ in
primary breast cancer (BC) correlates with expression of two major breast markers,
ERBB2 and oestrogen receptor. High AP-2γ expression is associated with reduced
survival in BC patients, including those treated with hormone therapy. Our aim is to
define the pathways regulated by AP-2 factors in breast epithelial cells. Data from
AP-2γ depleted MCF-7 cells suggested a role in cell cycle control. Here, regulation
by AP-2α and AP-2γ in additional breast cancer cell lines with differing genetic
background is investigated. Cell cycle analysis of synchronized T47D cells, which
express both AP-2 isoforms but mutant p53, showed a reduction in G1 but increased
S and G2/M-phase populations when AP-2α and AP-2γ were silenced either
independently or together. Despite the lack of growth arrest, p21cip protein levels
increased following AP-2 silencing. ChIP analysis showed AP-2α and AP-2γ binding
at the p21cip/CDKN1A promoter. In addition, cyclin D3 protein levels increased
following AP-2 silencing and ChIP analysis showed AP-2α and AP-2γ binding to its
promoter. Luciferase reporter constructs carrying CCND3 promoter sequences were
repressed when co-transfected with AP-2α or AP-2γ expression constructs. These
findings demonstrate the importance of AP-2 factors in the control of cell cycle
regulation but illustrate cell-type differences in their mode of action. Further work
focused on MCF10A immortalised breast epithelial cells, which express both AP-2
isoforms and wild-type p53. AP-2 silenced MCF10A cells adopted a more rounded
phenotype suggestive of changes in cell adhesion which was also supported by
microarray analysis of their gene expression profile.
KIAA1324, a protein of unknown function with features of a membrane-bound
growth factor receptor, was found to be significantly down-regulated following AP-
2γ silencing in MCF-7 cells. Functional assays using i) inducible knock down of
KIAA1324 in MCF-7 cells, and ii) stable KIAA1324 overexpression in MCF10A
investigated if altering KIAA1324 expression level could affect cell growth.
KIAA1324 did not affect breast epithelial cell proliferation on plastic but may
contribute to the ability of MCF-7 cells to display anchorage-independent growth
Memo re: Oflag 64
No full textCopy of letter from Col. Catesby ap C. Jones, chief of the Policy Group II in the U.S. War Department, to Colonel Thomas Drake, War Department general staff and former prisoner of war, regarding proposed letter written
A role for amphiphysin in AP-1/clathrin coat formation
No full textTransport of cargo within the endocytic and secretory pathway is generally mediated by coated vesicles. Clathrin, in combination with different adaptor proteins, is the major coat protein for vesicle formation at the plasma membrane, endosomes, and the trans-Golgi network (TGN). Best characterized is the formation of clathrin coats for endocytosis at the plasma membrane involving the adaptor protein complex AP-2. Clathrin and AP-2 were shown to be at the centre of a complex interactome of proteins accessory to vesicle formation. Considerably less is known about the formation of clathrin coated carriers at the TGN and endosomes, where the adaptor protein complex AP-1 plays a major role.
In vitro studies showed the minimal requirements for association of AP-1 to liposomal membranes to be activated ARF1, phosphoinositides, and either sorting signals or unknown cytosolic factors. We have used a liposome floatation assay to identify cytosolic proteins collaborating with AP-1 at the membrane. Separation of proteins from bovine brain cytosol with several chromatographic methods yielded an active fraction containing amphiphysin 1, amphiphysin 2, and endophilin A1. All three proteins are expressed in brain and known to be involved in AP-2/clathrin coat formation. They consist of an N-terminal N-BAR (Bin, amphiphysin, Rvs) domain for dimerization and membrane binding and a C-terminal SH3 (Src homology 3) domain for interaction with dynamin and synaptojanin. Amphiphysin 1 and 2 in addition contain a middle domain with binding sites for adaptors and clathrin. It was proposed that amphiphysins and endophilin are targeted to membranes with high curvature, such as the neck of a forming vesicle, where they recruit dynamin and synaptojanin in preparation for vesicle fission and uncoating.
In this thesis, I bacterially expressed and purified all three proteins and tested them in the floatation assay for AP-1 membrane binding activity. Only amphiphysin 2 showed activity, both as a homodimer and as a heterodimer with amphiphysin 1. Activity depended on a motif that was shown to bind to AP-1, AP-2, and clathrin in GST pull-down experiments.
Endogenous amphiphysins in primary neurons, as well as transiently expressed in neuronal or fibroblast cell lines, co-localized with AP-1 at the TGN. In addition, when expressed at high levels in neuronal cells, amphiphysins aggregated and interfered dominantly with the TGN localization of AP-1. Both phenomena depended on the presence of the clathrin and adaptor interaction sequence in the amphiphysins. Furthermore, both amphiphysins could be cross-linked to AP-1 in vivo.
Our results indicate that amphiphysin 1 and 2 function not only in clathrin coated vesicle formation for endocytosis at the plasma membrane, but are also part of the machinery forming AP-1/clathrin coats at the TGN and endosomes. This suggests that the machineries for CCV formation with AP-1 and AP-2 at different locations in the cell share more components than previously anticipated
Characterizing the role of p21-Activated Kinase 3 (PAK3) in AP-1-induced transformation
No full textIncludes bibliographical references.Previous studies identified p21-Activated Kinase 3 (PAK3), a serine/threonine kinase, as a potential AP-1 target gene. PAK3 has been implicated in a variety of pathological disorders and over-expression of other PAK-family members has been linked to cancer. In this study, we investigated AP-1 regulation of PAK3 expression and the role of PAK3 in cJun/AP-1-associated cellular transformation. Our results showed elevated PAK3 expression at both the mRNA and protein level in cJun-over-expressing Rat1a fibroblasts, as well as in transformed human fibroblasts. Elevated PAK3 protein levels were also seen in cervical, ovarian, oesophageal and breast cancer cells lines, while poor survival tracked with high PAK3 expression in ovarian cancer patient material. Elevated PAK3 levels appear to play no role in the proliferation of transformed or cancerous cells, however appears vital for the transformed morphology and actin distribution. These cytoskeletal changes seem to be the underlying force governing cellular migration, as inhibition of PAK3 significantly reduced the motility of both transformed fibroblasts and cancer cell lines. Our data shows that elevated PAK3 expression in response to AP-1 over-expression is regulated through the transcriptional activation of the PAK3 promoter by AP-1 binding directly to a single site in the promoter. We also show that constitutive activation of PAK3 results in changes in cJun phosphorylation and an increase in AP-1 activity, which can be inhibited by a serine/threonine kinase inhibitor. PAK3 and AP-1 proteins were also shown to directly interact with each other. Our study is a first to describe a role for AP-1 in regulating PAK3 expression, and PAK3 in regulating AP-1 activity, identifying a potential feedback loop in which PAK3 is an AP-1 target required for cytoskeletal reorganization and migration observed in transformed cells
Magnetic fields in axisymmetric neutron stars
No full textWe derive general equations for axisymmetric Newtonian magnetohydrodynamics and use these as the basis of a code for calculating equilibrium configurations of rotating magnetized neutron stars in a stationary state. We investigate the field configurations that result from our formalism, which include purely poloidal, purely toroidal and mixed fields. For the mixed-field formalism, the toroidal component appears to be bounded at less than 7 per cent. We calculate distortions induced both by magnetic fields and by rotation. From our non-linear work, we are able to look at the realm of validity of perturbative work: we find for our results that perturbative-regime formulae for magnetic distortions agree to within 10 per cent of the non-linear results if the ellipticity is less than 0.15 or the average field strength is less than 10^17 G. We also consider how magnetized equilibrium structures vary for different polytropic indices
Arthur Jones. — The history of Gruffydd ap Cynan, The Welsh text with translation, introduction and notes
No full textDottin Georges. Arthur Jones. — The history of Gruffydd ap Cynan, The Welsh text with translation, introduction and notes. In: Annales de Bretagne. Tome 26, numéro 2, 1910. p. 464
The Treatment of Ties in AP Correlation
No full textThe Kendall tau and AP correlation coefficients are very commonly use to compare two rankings over the same set of items. Even though Kendall tau was originally defined assuming that there are no ties in the rankings, two alternative versions were soon developed to account for ties in two different scenarios: measure the accuracy of an observer with respect to a true and objective ranking, and measure the agreement between two observers in the absence of a true ranking. These two variants prove useful in cases where ties are possible in either ranking, and may indeed result in very different scores. AP correlation was devised to incorporate a top-heaviness component into Kendall tau, penalizing more heavily if differences occur between items at the top of the rankings, making it a very compelling coefficient in Information Retrieval settings. However, the treatment of ties in AP correlation remains an open problem. In this paper we fill this gap, providing closed analytical formulations of AP correlation under the two scenarios of ties contemplated in Kendall tau. In addition,we developed an R package that implements these coefficients.Best Short Paper Accepted author manuscriptMultimedia ComputingWeb Information System
Delamination Analysis of A Class of AP-PLY Composite Laminates
No full textA recently developed fiber placement architecture, AP-PLY, has been shown to give significantly improved damage tolerance characteristics of composite structures. The behavior of delaminations resulting from low speed impact damage is of particular concern. Major attention has been paid to expand current knowledge on the delamination response of simple AP-PLY composite structure and move towards in-depth understanding of the failure mechanisms behind the damage tolerance. This thesis presents the approaches to predict delamination onset and analyze delamination growth, in support of the search of the optimum woven pattern for AP-PLY composite laminates. The recovered interlaminar stress between layers combined with the maximum stress criterion determined the delamination onset of simple AP-PLY composite laminate under out-of-plane loads. 2D finite element models with cohesive elements inserted in the interfaces of woven layers have been built to evaluate the delamination initiation and propagation in the different woven patterns of simple AP-PLY composite beams. The parameters of the woven pattern, such as the woven angle, the number of woven plies, the number of straight filled plies, and the location of the woven patterns in through the thickness direction, were investigated and shown to have a significant effect on delamination creation and growth. An energy method based on beam theory was proposed to analyze the strain energy release rate (SERR) of an existing crack in an AP-PLY beam structure. The developed analytical method was implemented in isotropic materials and the obtained SERR of a crack was validated by reference results and finite element solutions. The general behavior of crack growth on the left or right crack tip was evaluated and basic trends leading to crack propagation on one side of the crack were established. A correction factor was introduced to improve the accuracy of the SERR of a small crack through the numerical calculation. The singularity of crack tip caused by dissimilar materials was investigated and was found that the inclusion of the singularity effect could increase the accuracy for small cracks. It has been shown that the neutral axis needs to be relocated to decouple the bending and membrane behavior of unsymmetrical composite laminates, thus to meet the requirement of minimizing the strain energy of the delaminated beam to calculate the SERR of a delaminated composite beam. The calculated SERR of a crack in a composite beam has been verified by comparing with a finite element model. The woven plies in AP-PLY composite laminate altered the layup and two conventional laminates with different stacking sequences were identified in an AP-PLY composite laminate based on the assumption that the resin areas were ignored. A step by step approach was developed to obtain the SERR of a crack that goes across different materials. The analytical SERR determined when two materials are used in sequence, sets the stage for optimization of AP-PLY composite laminates without taking account of the effect of the resin area. The procedure of optimization of simple AP-PLY pattern was proposed and industry may benefit for many applications. An equivalent stiffness approach was used to model regions containing resin pockets and straight or inclined composite layers. A series of three point bending tests was carried out where the failure process and loading capacity were evaluated. The methodology, procedure of optimization, philosophy outlined in this thesis might also be applied to the more complicated fully woven AP-PLY composite laminates. The work in this thesis contributes to the understanding of the behavior of AP-PLY composite laminates with delaminations
- …
