1,468 research outputs found

    Bounds for the Twin-width of Graphs

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    Bonnet, Kim, Thomass\'{e}, and Watrigant (2020) introduced the twin-width of a graph. We show that the twin-width of an nn-vertex graph is less than (n+nlnn+n+2lnn)/2(n+\sqrt{n\ln n}+\sqrt{n}+2\ln n)/2, and the twin-width of an mm-edge graph for a positive mm is less than 3m+m1/4lnm/(431/4)+3m1/4/2\sqrt{3m}+ m^{1/4} \sqrt{\ln m} / (4\cdot 3^{1/4}) + 3m^{1/4} / 2. Conference graphs of order nn (when such graphs exist) have twin-width at least (n1)/2(n-1)/2, and we show that Paley graphs achieve this lower bound. We also show that the twin-width of the Erd\H{o}s-R\'{e}nyi random graph G(n,p)G(n,p) with 1/np=p(n)1/21/n\leq p=p(n)\leq 1/2 is larger than 2p(1p)n(22+ε)p(1p)nlnn2p(1-p)n - (2\sqrt{2}+\varepsilon)\sqrt{p(1-p)n\ln n} asymptotically almost surely for any positive ε\varepsilon. Lastly, we calculate the twin-width of random graphs G(n,p)G(n,p) with pc/np\leq c/n for a constant c<1c<1, determining the thresholds at which the twin-width jumps from 00 to 11 and from 11 to 22.Comment: 22 pages, 1 figur

    Pyruvate kinase isozyme type M2 (PKM2) interacts and cooperates with Oct-4 in regulating transcription

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    The Oct-4 gene encodes a transcription factor that plays an important role in maintaining the pluripotent state of embryonic stem cells and may prevent expression of genes activated during differentiation. Although its role in maintaining embryonic stem cell pluripotency is well established, there is still little known about the binding partners that regulate its function. To identify proteins that control Oct-4 function, we used affinity chromatography on immobilized Oct-4 (POU) together with MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS (mass spectrometry) and isolated a novel Oct-4-interacting protein, pyruvate kinase type M2 (PKM2 or M2-PK). PKM2 is an isozyme of pyruvate kinase that is specifically expressed in proliferating cells, such as embryonic stem cells, embryonic carcinoma cells, as well as cancer cells. Oct-4 and PKM2 were co-affinity precipitated from cell extracts, and glutathione S-transferase pull-down assays revealed that the POU DNA binding domain of Oct-4 was required for interaction with PKM2. In addition, the C-terminal domain of PKM2 (amino acids 307-531) was involved in binding to Oct-4. Moreover, ectopic expression of the PKM2 enhanced Oct-4-mediated transcription. These observations indicate that the transactivation potential of the Oct-4 transcription factor is positively modulated by PKM2. (C) 2007 Elsevier Ltd. All rights reserved.This research was supported by a grant (SC2090) from the Stem Cell Research Center of the 21st Century Frontier Research Program funded by the Ministry of Science and Technology, Republic of Korea, by a grant (Code #20070501034009) from BioGreen21 Program, Rural Development Administration, Republic of Korea, and by the Seoul Research and Business Development Program (10816), Republic of Korea. JL was a recipient of Seoul Science Fellowships and of a research fellowship BK21 from the Ministry of Education and Human Resources Development
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