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7. OPTHiS Identifies the Molecular Basis of the Direct Interaction between CSL and SMRT Corepressor

Author

Kim, Gwang Sik, Park, Hee-Sae, and Lee, Young Chul

Subjects
Notch, Receptors, Notch, Intracellular Signaling Peptides and Proteins, Muscle Proteins, LIM Domain Proteins, Article, Neoplasm Proteins, DNA-Binding Proteins, HEK293 Cells, Immunoglobulin J Recombination Signal Sequence-Binding Protein, Two-Hybrid System Techniques, Mutation, CSL, Animals, Humans, Nuclear Receptor Co-Repressor 2, Amino Acid Sequence, Protein Interaction Maps, ϕWϕP motif, OPTHiS, SMRT, Sequence Alignment, Plasmids, Protein Binding
Abstract

Notch signaling is an evolutionarily conserved pathway and involves in the regulation of various cellular and developmental processes. Ligand binding releases the intracellular domain of Notch receptor (NICD), which interacts with DNA-bound CSL [CBF1/Su(H)/Lag-1] to activate transcription of target genes. In the absence of NICD binding, CSL down-regulates target gene expression through the recruitment of various corepressor proteins including SMRT/NCoR (silencing mediator of retinoid and thyroid receptors/nuclear receptor corepressor), SHARP (SMRT/HDAC1-associated repressor protein), and KyoT2. Structural and functional studies revealed the molecular basis of these interactions, in which NICD coactivator and corepressor proteins competitively bind to β-trefoil domain (BTD) of CSL using a conserved ϕWϕP motif (ϕ denotes any hydrophobic residues). To date, there are conflicting ideas regarding the molecular mechanism of SMRT-mediated repression of CSL as to whether CSL-SMRT interaction is direct or indirect (via the bridge factor SHARP). To solve this issue, we mapped the CSL-binding region of SMRT and employed a ‘one- plus two-hybrid system’ to obtain CSL interaction-defective mutants for this region. We identified the CSL-interaction module of SMRT (CIMS; amino acid 1816–1846) as the molecular determinant of its direct interaction with CSL. Notably, CIMS contains a canonical ϕWϕP sequence (APIWRP, amino acids 1832–1837) and directly interacts with CSL-BTD in a mode similar to other BTD-binding corepressors. Finally, we showed that CSL-interaction motif, rather than SHARP-interaction motif, of SMRT is involved in transcriptional repression of NICD in a cell-based assay. These results strongly suggest that SMRT participates in CSL-mediated repression via direct binding to CSL.

Published
2018

12. Steep‐Slope Gate‐Connected Atomic Threshold Switching Field‐Effect Transistor with MoS2 Channel and Its Application to Infrared Detectable Phototransistors.

Author

Kim, Seung‐Geun, Kim, Seung‐Hwan, Kim, Gwang‐Sik, Jeon, Hyeok, Kim, Taehyun, and Yu, Hyun‐Yong

Subjects
FIELD-effect transistors, PHOTOTRANSISTORS, TRANSISTORS, METAL oxide semiconductor field-effect transistors
Abstract

For next‐generation electronics and optoelectronics, 2D‐layered nanomaterial‐based field effect transistors (FETs) have garnered attention as promising candidates owing to their remarkable properties. However, their subthreshold swings (SS) cannot be lower than 60 mV/decade owing to the limitation of the thermionic carrier injection mechanism, and it remains a major challenge in 2D‐layered nanomaterial‐based transistors. Here, a gate‐connected MoS2 atomic threshold switching FET using a nitrogen‐doped HfO2‐based threshold switching (TS) device is developed. The proposed device achieves an extremely low SS of 11 mV/decade and a high on‐off ratio of ≈106 by maintaining a high on‐state drive current due to the steep switching of the TS device at the gate region. In particular, the proposed device can function as an infrared detectable phototransistor with excellent optical properties. The proposed device is expected to pave the way for the development of future 2D channel‐based electrical and optical transistors. [ABSTRACT FROM AUTHOR]

Published
2021
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38. Infrared Detectable MoS2Phototransistor and Its Application to Artificial Multilevel Optic-Neural Synapse

Author

Kim, Seung-Geun, Kim, Seung-Hwan, Park, June, Kim, Gwang-Sik, Park, Jae-Hyeun, Saraswat, Krishna C., Kim, Jiyoung, and Yu, Hyun-Yong

Abstract

Layered two-dimensional (2D) materials have entered the spotlight as promising channel materials for future optoelectronic devices owing to their excellent electrical and optoelectronic properties. However, their limited photodetection range caused by their wide bandgap remains a principal challenge in 2D layered materials-based phototransistors. Here, we developed a germanium (Ge)-gated MoS2phototransistor that can detect light in the region from visible to infrared (λ = 520–1550 nm) using a detection mechanism based on band bending modulation. In addition, the Ge-gated MoS2phototransistor is proposed as a multilevel optic-neural synaptic device, which performs both optical-sensing and synaptic functions on one device and is operated in different current ranges according to the light conditions: dark, visible, and infrared. This study is expected to contribute to the development of 2D material-based phototransistors and synaptic devices in next-generation optoelectronics.

Published
2019
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48. Reduction of Threshold Voltage Hysteresis of MoS2Transistors with 3-Aminopropyltriethoxysilane Passivation and Its Application for Improved Synaptic Behavior

Author

Han, Kyu Hyun, Kim, Gwang-Sik, Park, June, Kim, Seung-Geun, Park, Jin-Hong, and Yu, Hyun-Yong

Abstract

Although molybdenum disulfide (MoS2) is highlighted as a promising channel material, MoS2-based field-effect transistors (FETs) have a large threshold voltage hysteresis (ΔVTH) from interface traps at their gate interfaces. In this work, the ΔVTHof MoS2FETs is significantly reduced by inserting a 3-aminopropyltriethoxysilane (APTES) passivation layer at the MoS2/SiO2gate interface owing to passivation of the interface traps. The ΔVTHis reduced from 23 to 10.8 V by inserting the 1%-APTES passivation layers because APTES passivation prevents trapping and detrapping of electrons, which are the major source of the ΔVTH. The reduction in the density of interface traps (Dit) is confirmed by the improvement of the subthreshold swing (SS) after inserting the APTES layer. Furthermore, the improvement in the synaptic characteristics of the MoS2FET through the APTES passivation is investigated. Both inhibitory and excitatory postsynaptic currents (PSC) are increased by 33% owing to the reduction in the ΔVTHand the n-type doping effect of the APTES layer; moreover, the linearity of PSC characteristics is significantly improved because the reduction in ΔVTHenables the synaptic operation to be over the threshold region, which is linear. The application of the APTES gate passivation technique to MoS2FETs is promising for reliable and accurate synaptic applications in neuromorphic computing technology as well as for the next-generation complementary logic applications.

Published
2019
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49. Schottky Barrier Height Modulation Using Interface Characteristics of MoS2Interlayer for Contact Structure

Author

Kim, Seung-Hwan, Han, Kyu Hyun, Kim, Gwang-Sik, Kim, Seung-Geun, Kim, Jiyoung, and Yu, Hyun-Yong

Abstract

Schottky barrier height (SBH) engineering of contact structures is a primary challenge to achieve high performance in nanoelectronic and optoelectronic applications. Although SBH can be lowered through various Fermi-level (FL) unpinning techniques, such as a metal/interlayer/semiconductor (MIS) structure, the room for contact metal adoption is too narrow because the work function of contact metals should be near the conduction band edge (CBE) of the semiconductor to achieve low SBH. Here, we propose a novel structure, the metal/transition metal dichalcogenide/semiconductor structure, as a contact structure that can effectively lower the SBH with wide room for contact metal adoption. A perpendicularly integrated molybdenum disulfide (MoS2) interlayer effectively alleviates FL pinning by reducing metal-induced gap states at the MoS2/semiconductor interface. Additionally, it can induce strong FL pinning of contact metals near its CBE at the metal/MoS2interface. The technique using FL pinning and unpinning at metal/MoS2/semiconductor interfaces is first introduced in the MIS scheme to allow the use of various contact metals. Consequently, significant reductions of the SBH from 0.48 to 0.12 eV for GaAs and from 0.56 to 0.10 eV for Ge are achieved with several different contact metals. This work significantly reduces the dependence on contact metals with lowest SBH and proposes a new way of overcoming current severe contact issues for future nanoelectronic and optoelectronic applications.

Published
2019
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