Thyroid Hormone Receptor Nucleocytoplasmic Transport

The thyroid hormone receptor α1 (TRα1) and the thyroid hormone receptor β1 (TRβ1) are transcription factors that modulate the expression of target genes that are important in metabolism and development in response to thyroid hormone. Although primarily localized to the nucleus, prior studies have shown that TRα1 and TRβ1 shuttle rapidly between the nucleus and cytoplasm, and that nuclear import of TRα1 is directed by two nuclear localization signal (NLS) motifs: NLS-1 in the hinge domain, and NLS-2 in the N-terminal A/B domain. In contrast, TRβ1 lacks NLS-2. Previous studies also characterized two nuclear export signal (NES) motifs, NES-H3/H6 and NES-H12, that reside in the ligand-binding domain and mediate TR nuclear export. Here, we investigated which importins mediate nuclear import of TRa1 using a combined approach of shRNA-mediated knockdown and coimmunoprecipitation assays in HeLa (human) cells. Among all the importins we tested in transient transfection assays (importins 4, 5, 6, 7, 8, 9, 13, importin β1, and adaptor importin α variants), only importin 7, importin β1, and adaptor importin α1 knockdown experiments resulted in a significant localization pattern change from primarily nuclear to a more cytosolic distribution of TRα1. to demonstrate direct interaction between TRα1 or TRβ1 and these importins, “GFP-trap” co-immunoprecipitation assays were performed. Importin 7, importin β1, and adaptor importin α1 were shown to interact with TRα1, while importin 4 as a negative control, did not. Our data show that nuclear entry of TRα1 in HeLa cells is facilitated by both importin 7, likely through interactions with NLS-2, and importin β1 and the adapter importin α1 interacting with NLS-1 and NLS-2. In contrast, TRα1 nuclear import is facilitated only by importin α1/β1 interacting with NLS-1. Prior results from knockdown and overexpression studies provided evidence that multiple exportins influence TR localization. Here, we investigated which exportins serve as a direct carrier for each of the multiple NES motifs in TRα1, using “GFP-trap” coimmunoprecipitation assays. The information would be provided in Chapter 5. Consistent with our prior studies, results show protein-protein interactions between TRα1 and XPO4, XPO5, and XPO7, but not with XPO6. Taken together, our findings highlight a fine balance of nuclear import, retention, and export that modulates TR function

Fine timing synchronization based on modified expectation maximization clustering algorithm for OFDM systems

A novel fine timing synchronization method based on the modified expectation-maximization (EM) clustering algorithm is proposed for orthogonal frequency-division multiplexing systems. Using the cross-correlation metrics of one preamble symbol, the cross-correlation peaks corresponding to the channel arriving paths are identified by the proposed modified EM clustering algorithm, the position of the first coherent cross-correlation peak is then chosen as the start of the frame. Computer simulations show that the proposed method is robust in multipath dispersive channels and achieves superior performance to existing techniques in terms of timing accuracy

Elucidating the Biological Functions of YEATS Domain Containing Proteins in Metabolism Driven Transcriptional Regulation

DNA is the fundamental basis of our genetic information. Throughout evolution, cells have adapted mechanisms that not only allow compaction of DNA into the nucleus, but also maintain easy access to DNA for precise replication, transcription, and damage repair. DNA is wrapped around histone octamers to form nucleosomes, and then a higher-order structure called chromatin. It was revealed that chromatin has regulatory functions for transcription and other biological processes due to its dynamic quality. In eukaryotic organisms, gene regulation is about the balance between compacted DNA and gaining access for RNA polymerase and other regulatory proteins. As the most basic unit of chromatin, a nucleosome has two copies of canonical histones H2A, H2B, H3 and H4 with a segment of about 147 base pairs of DNA. Canonical histones are only expressed in certain times of the cell cycle and they are incorporated into the newly replicated genome. In contrast, histone variants are expressed throughout the cell cycle and are deposited when canonical histones are removed. Histone variants, such as H2A.Z, affect nucleosome properties with distinct modifiable amino acid sequences. Chromatin function is influenced by histone post-translational modifications (PTMs), which can act in a sequential or combinatorial fashion to influence downstream functions. It has been widely acknowledged that histone PTMs such as histone acetylation, crotonylation, and methylation play crucial roles in various biological processes including gene transcription, DNA repair, gene replication, and apoptosis. Additionally, the precursors of histone acetylation and crotonylation, acetyl-CoA and crotonyl-CoA, are regulated by cellular metabolism. This argues that the transcriptional regulatory functions from both PTMs are influenced by cellular metabolism. In recent years, YEATS-domain proteins have gained more appreciation due to their ability to bind both acetylation and crotonylation. As acyllysine readers, YEATS domain proteins amplify the impact of histone acylations on transcriptional regulation through communicating with various transcriptional factors. In budding yeast, there are three YEATS domain proteins: Yaf9, Taf14, and Sas5. Each of them is involved in various essential processes and shows binding preference for specific acylations. Previous work has demonstrated that the YEATS domain of Taf14 binding to crotonylated histone lysine down-regulates pro-growth gene expression during the low oxygen consumption phase, suggesting that transcription is regulated by cellular metabolism through the interactions between YEATS domain and acylation. The work in this dissertation focuses on another YEATS domain protein, Yaf9, and discusses the role it plays in connecting gene expression and cellular metabolism.Doctor of Philosoph

Model classification-and-selection assisted robust receiver for OFDM systems

This paper devises a robust receiver for OFDM systems in the presence of residual timing offsets and unknown channel prior information. The proposed receiver constructs typical receiver models and resorts to the model selection technique to choose the best-matched receiver model to improve the channel estimation and signal detection. The typical receiver models are classified by considering the channel delay spread and the level of timing offset. Based on the receiver model selected by the Bayesian model selection algorithm, the channel length and timing offset parameters in the receiver model can provide the effective channel statistical information to make the channel estimator adapt to the altered circumstances and thus more accurate. Furthermore, the effective interference variance parameters in the selected receiver model are used to enhance the channel estimation and refine the soft symbol detection. The simulation results show that the proposed receiver achieves a significant performance gain compared to the existing methods. It is also shown that the proposed scheme makes the receiver robust to the diverse channel conditions and the timing offset states at a cost of the only a moderate increase in complexity

Peak-to-average power ratio analysis for OFDM-based mixed-numerology transmissions

In this paper, the probability distribution of the peak to average power ratio (PAPR) is analyzed for the mixed numerologies transmission based on orthogonal frequency division multiplexing (OFDM). State of the art theoretical analysis implicitly assumes continuous and symmetric frequency spectrum of OFDM signals. Thus, it is difficult to be applied to the mixed-numerology system due to its complication. By comprehensively considering system parameters, including numerology, bandwidth and power level of each subband, we propose a generic analytical distribution function of PAPR for continuous-time signals based on level-crossing theory. The proposed approach can be applied to both conventional single numerology and mixed-numerology systems. In addition, it also ensures the validity for the noncontinuous-OFDM (NC-OFDM). Given the derived distribution expression, we further investigate the effect of power allocation between different numerologies on PAPR. Simulations are presented and show the good match of the proposed theoretical results

Structure-based Discovery of Novel Small Molecule Wnt Signaling Inhibitors by Targeting the Cysteine-rich Domain of Frizzled.

Frizzled is the earliest discovered glycosylated Wnt protein receptor and is critical for the initiation of Wnt signaling. Antagonizing Frizzled is effective in inhibiting the growth of multiple tumor types. The extracellular N terminus of Frizzled contains a conserved cysteine-rich domain that directly interacts with Wnt ligands. Structure-based virtual screening and cell-based assays were used to identify five small molecules that can inhibit canonical Wnt signaling and have low IC50 values in the micromolar range. NMR experiments confirmed that these compounds specifically bind to the Wnt binding site on the Frizzled8 cysteine-rich domain with submicromolar dissociation constants. Our study confirms the feasibility of targeting the Frizzled cysteine-rich domain as an effective way of regulating canonical Wnt signaling. These small molecules can be further optimized into more potent therapeutic agents for regulating abnormal Wnt signaling by targeting Frizzled

FAHP and TOPSIS Prediction of Diamond Segments Wear When Using Frame Saw to Cut Granites

Fuzzy Analytic Hierarchy Process (FAHP) and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) approaches were employed to predict the sawability of a diamond frame saw to cut granites. FAHP is used to determine the weights of the criteria of decision-makers and TOPSIS is used to rank sawability. The sawability was evaluated by diamond segment wear. The prediction of segment wear is important to determine the segments service life and sawing cost and may determine cutting parameter selection for a given stone. Sawing experiments were conducted to verify the analysis result of the applied method in this study. The experimental results are in good agreement with the theoretical analysis. The ranking method can be used to evaluate segment wear. Stone properties, such as uniaxial compressive strength, shore hardness, quartz content, and bending strength, must be determined for the best segment wear ranking