The second AT-hook of the architectural transcription factor HMGA2 is determinant for nuclear localization and function

High Mobility Group A (HMGA) is a family of architectural nuclear factors which play an important role in neoplastic transformation. HMGA proteins are multifunctional factors that associate both with DNA and nuclear proteins that have been involved in several nuclear processes including transcription. HMGA localization is exclusively nuclear but, to date, the mechanism of nuclear import for these proteins remains unknown. Here, we report the identification and characterization of a nuclear localization signal (NLS) for HMGA2, a member of the HMGA family. The NLS overlaps with the second of the three AT-hooks, the DNA-binding domains characteristic for this group of proteins. The functionality of this NLS was demonstrated by its ability to target a heterologous β-galactosidase/green fluorescent protein fusion protein to the nucleus. Mutations to alanine of basic residues within the second AT-hook resulted in inhibition of HMGA2 nuclear localization and impairment of its function in activating the cyclin A promoter. In addition, HMGA2 was shown to directly interact with the nuclear import receptor importin-α2 via the second AT-hook. HMGA proteins are overexpressed and rearranged in a variety of tumors; our findings can thus help elucidating their role in neoplastic transformation

Basic residues of the second AT-hook of HMGA2 are responsible for nuclear localization of fusion proteins

<p><b>Copyright information:</b></p><p>Taken from "The second AT-hook of the architectural transcription factor HMGA2 is determinant for nuclear localization and function"</p><p></p><p>Nucleic Acids Research 2007;35(6):1751-1760.</p><p>Published online 25 Feb 2007</p><p>PMCID:PMC1874589.</p><p>© 2007 The Author(s)</p> () Partial sequences of point-mutated constructs of HMGA2. Basic residues were replaced with alanine residues as indicated. Each point-mutant is fused C-terminally with EGFP (not drawn); numbers identify positions of residues on HMGA2 protein sequence. Summary of intracellular localization is indicated at right. () NIH-3T3 cells were transfected with HMGA2 point-mutant constructs, and fusion proteins were visualized by confocal laser microscopy. Propidium iodide (PI) staining of the same nuclei is shown. At least one hundred cells per transfection were analyzed in three different experiments, and at least one hundred cells per transfection were subjected to fluorescence quantification. Bars, 10 μm. () For each point-mutant construct, nuclear and cytoplasmic fluorescence were quantified, and percentage of nuclear localization was calculated. Bars indicate percentage ± standard deviation. () The expression and integrity of the fusion proteins were analyzed by Western blot using anti-GFP antibody

HMGA2-mediated transcriptional activation is dependent upon basic residues within the second AT-hook

<p><b>Copyright information:</b></p><p>Taken from "The second AT-hook of the architectural transcription factor HMGA2 is determinant for nuclear localization and function"</p><p></p><p>Nucleic Acids Research 2007;35(6):1751-1760.</p><p>Published online 25 Feb 2007</p><p>PMCID:PMC1874589.</p><p>© 2007 The Author(s)</p> () Diagram of luciferase reporter gene under the transcriptional regulation of the cyclin A promoter and the HMGA2 wild type and mutants expressed by the vectors used. () CHO cells were transiently cotransfected with 1 µg of the CycA luciferase reporter plasmid (bars 1–4) and with 3 µg of HMGA2 wt-, mS5- and mT6- EGFP expression vectors (bars 2–4 respectively). 0.1 µg of pRL-CMV Renilla luciferase expression vector was included to normalize for transfection efficiencies. Values are reported as relative luciferase activity. Standard deviations are indicated for experiments repeated three times. The amount of HMGA2 wt-, mS5- and mT6-EGFP expression was assayed by Western blot analysis using a polyclonal α-HMGA2 antibody. The subcellular localization of the expressed proteins in CHO cells was confirmed by confocal microscopy (data not shown)

Identification of HMGA2 nuclear localization signal by deletion mutagenesis

<p><b>Copyright information:</b></p><p>Taken from "The second AT-hook of the architectural transcription factor HMGA2 is determinant for nuclear localization and function"</p><p></p><p>Nucleic Acids Research 2007;35(6):1751-1760.</p><p>Published online 25 Feb 2007</p><p>PMCID:PMC1874589.</p><p>© 2007 The Author(s)</p> () Schematic representation of HMGA2 deletion mutants; each deletion mutant is fused to β-gal at the N-terminus, and to GFP at the C-terminus. Summary of intracellular localization is indicated at the right. () NIH-3T3 cells were transfected with HMGA2 deletion mutants constructs, and fusion proteins were visualized by confocal laser microscopy. Propidium iodide (PI) staining of the same nuclei is shown. At least one hundred cells per transfection were analyzed in three different experiments. Bars, 10 μm. () Western blot analysis performed with an anti-GFP antibody

Studying the interaction between charm and light-flavor mesons

International audienceThe two-particle momentum correlation functions between charm mesons ($\mathrm{D^{*\pm}}$ and $\mathrm{D}^\pm$) and charged light-flavor mesons ($\pi^{\pm}$ and K$^{\pm}$) in all charge-combinations are measured for the first time by the ALICE Collaboration in high-multiplicity proton-proton collisions at a center-of-mass energy of $\sqrt{s} =13$ TeV. For $\mathrm{DK}$ and $\mathrm{D^*K}$ pairs, the experimental results are in agreement with theoretical predictions of the residual strong interaction based on quantum chromodynamics calculations on the lattice and chiral effective field theory. In the case of $\mathrm{D}\pi$ and $\mathrm{D^*}\pi$ pairs, tension between the calculations including strong interactions and the measurement is observed. For all particle pairs, the data can be adequately described by Coulomb interaction only, indicating a shallow interaction between charm and light-flavor mesons. Finally, the scattering lengths governing the residual strong interaction of the $\mathrm{D}\pi$ and $\mathrm{D^*}\pi$ systems are determined by fitting the experimental correlation functions with a model that employs a Gaussian potential. The extracted values are small and compatible with zero

Measurement of the production cross section of prompt Ξ0c baryons in p–Pb collisions at √sNN = 5.02 TeV

The transverse momentum (pT) differential production cross section of the promptly-produced charm-strange baryon Ξ0c (and its charge conjugate Ξ0c¯¯¯¯¯¯) is measured at midrapidity via its hadronic decay into π+Ξ− in p−Pb collisions at a centre-of-mass energy per nucleon−nucleon collision sNN−−−√ = 5.02 TeV with the ALICE detector at the LHC. The Ξ0c nuclear modification factor (RpPb), calculated from the cross sections in pp and p−Pb collisions, is presented and compared with the RpPb of Λ+c baryons. The ratios between the pT-differential production cross section of Ξ0c baryons and those of D0 mesons and Λ+c baryons are also reported and compared with results at forward and backward rapidity from the LHCb Collaboration. The measurements of the production cross section of prompt Ξ0c baryons are compared with a model based on perturbative QCD calculations of charm-quark production cross sections, which includes only cold nuclear matter effects in p−Pb collisions, and underestimates the measurement by a factor of about 50. This discrepancy is reduced when the data is compared with a model in which hadronisation is implemented via quark coalescence. The pT-integrated cross section of prompt Ξ0c-baryon production at midrapidity extrapolated down to pT = 0 is also reported. These measurements offer insights and constraints for theoretical calculations of the hadronisation process. Additionally, they provide inputs for the calculation of the charm production cross section in p−Pb collisions at midrapidity

Measurement of Ω0c baryon production and branching-fraction ratio BR(Ω0c → Ω−e+νe)/BR(Ω0c → Ω−π+) in pp collisions at √s = 13 TeV

The inclusive production of the charm-strange baryon Ω0c is measured for the first time via its semileptonic decay into Ω−e+νe at midrapidity (|y| < 0.8) in proton–proton (pp) collisions at the centre-of-mass energy √s = 13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2 < pT < 12 GeV/c. The branching-fraction ratio BR(Ω0c → Ω−e+νe)/BR(Ω0c → Ω−π+) is measured to be 1.12 ± 0.22 (stat.) ± 0.27 (syst.). Comparisons with other experimental measurements, as well as with theoretical calculations, are presented

Investigating the nature of the K0∗(700)^*_0(700) state with π±\pi^\pmKS0^0_{\rm S} correlations at the LHC

International audienceThe first measurements of femtoscopic correlations with the particle pair combinations $\pi^\pm$K$^0_{\rm S}$ in pp collisions at $\sqrt{s}=13$ TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K$^*_0(700)$ particle that has been considered a tetraquark candidate for over forty years. Boson source parameters and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, decaying into a $\pi^\pm$K$^0_{\rm S}$ pair. The extracted mass and Breit-Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K$^*_0(700)$. The small value and increasing behavior of the correlation strength with increasing source size support the hypothesis that the K$^*_0(700)$ is a four-quark state, i.e. a tetraquark state. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K$^*_0(700)$ resonance

Measurement of Ωc0\Omega^0_{\rm c} baryon production and branching-fraction ratio BR(Ωc0→Ω−e+νe)/BR(Ωc0→Ω−π+){\rm BR(\Omega^0_c \rightarrow \Omega^- e^+\nu_e)} / {\rm BR(\Omega^0_c \rightarrow \Omega^- \pi^+)} in pp collisions at s\sqrt{s} = 13 TeV

International audienceThe inclusive production of the charm-strange baryon $\Omega^{0}_{\rm c}$ is measured for the first time via its semileptonic decay into $\Omega^{-}\rm e^{+}\nu_{e}$ at midrapidity ($|y|<0.8$) in proton$-$proton (pp) collisions at the centre-of-mass energy $\sqrt{s}=13$ TeV with the ALICE detector at the LHC. The transverse momentum ($p_{\rm T}$) differential cross section multiplied by the branching ratio is presented in the interval $2<p_{\rm T}<12~{\rm GeV}/c$. The branching-fraction ratio ${\rm BR}(\Omega^0_{\rm c} \rightarrow \Omega^{-}{\rm e}^{+}\nu_{\rm e})/ {\rm BR}(\Omega^0_{\rm c} \rightarrow \Omega^{-}{\pi}^{+})$ is measured to be 1.12 $\pm$ 0.22 (stat.) $\pm$ 0.27 (syst.). Comparisons with other experimental measurements, as well as with theoretical calculations, are presented