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Byline: Wai Ho Li (Intelligent Robotics Research Centre, Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Victoria 3800, Australia, Wai.Ho.Li@eng.monash.edu.au); Alan M. Zhang (Intelligent Robotics Research Centre, Department [...]

Transforming growth factor beta (TGF-β)/bone morphogenetic protein (BMP) family ligands interact with specific membrane receptor complexes that have serine/threonine kinase activities. The receptor phosphorylation and activation induced by the ligands leads to phosphorylation of the Smad proteins, which translocate to the nucleus, controlling gene expression. Thus, regulation of Smad proteins is a key step in TGF-β/BMP-induced signal transduction. Here we report a novel mechanism of the regulation of SMAD-mediated signaling, by which the Smad1 protein level is controlled through expression of the CHIP protein. CHIP is a U-box-dependent E3 ubiquitin ligase, previously identified as a cochaperon protein. However, we have isolated CHIP as a Smad-interacting protein in a yeast two-hybrid screen using Smad1 as bait. Furthermore we have shown CHIP-Smad interaction using the [sup 35]S-labeled CHIP protein, which can interact with glutathione S-transferase (GST)-Smad1 and GST-Smad4 in an in vitro protein-binding assay. The CHIP-Smad interaction has been confirmed in vivo in mammalian cells through coimmunoprecipitation. Interestingly, we demonstrate that the coexpression of Smad1 and Smad4 with the CHIP protein results in the degradation of the Smad proteins through a ubiquitin-mediated process. Consistent with the observation that CHIP induces Smad1 degradation, we further show that the expression of CHIP can inhibit the transcriptional activities of the Smad1/Smad4 complex induced by BMP signals. Intriguingly, pBS/U6/CHIPi, which diminishes CHIP expression, significantly enhanced Smad1/Smad4- or BMPRIB(QD)-induced gene transcription. These results suggest that CHIP can interact with the Smad1/Smad4 proteins and block BMP signal transduction through the ubiquitin-mediated degradation of Smad proteins. [ABSTRACT FROM AUTHOR]

Bilateral symmetry is a salient visual feature of many man-made objects. In this paper, we present research that uses bilateral symmetry to identify, segment and track objects in real time using vision. Apart from the assumption of symmetry, the algorithms presented do not re- quire any object models, such as color shape or three-dimensional primitives. In order to counter the high computational cost of traditional symmetry detection methods, a novel computationally efficient algorithm is proposed. To investigate symmetry as an object feature, our fast detection scheme is applied to the tasks of object detection, segmentation and tracking. We find that objects with a line of symmetry can be segmented without relying on color or shape models by using a dynamic programming approach. Object tracking is achieved by estimating symmetry line parameters using a Kalman filter. The tracker operates at 40 frames per second on 640 × 480 video while running on a standard laptop PC. We use 10 difficult real-world tracking sequences to test our approach. We also quantitatively analyze symmetry as a tracking feature by comparing detected symmetry lines against ground truth. Color tracking is also performed to provide a qualitative comparison. [ABSTRACT FROM AUTHOR]