TY  - JOUR
A1  - Sander, Bodo
A1  - Xu, Wenshan
A1  - Eilers, Martin
A1  - Popov, Nikita
A1  - Lorenz, Sonja
T1  - A conformational switch regulates the ubiquitin ligase HUWE1
JF  - eLife
N2  - The human ubiquitin ligase HUWE1 has key roles in tumorigenesis, yet it is unkown how its activity is regulated. We present the crystal structure of a C-terminal part of HUWE1, including the catalytic domain, and reveal an asymmetric auto-inhibited dimer. We show that HUWE1 dimerizes in solution and self-associates in cells, and that both occurs through the crystallographic dimer interface. We demonstrate that HUWE1 is inhibited in cells and that it can be activated by disruption of the dimer interface. We identify a conserved segment in HUWE1 that counteracts dimer formation by associating with the dimerization region intramolecularly. Our studies reveal, intriguingly, that the tumor suppressor p14ARF binds to this segment and may thus shift the conformational equilibrium of HUWE1 toward the inactive state. We propose a model, in which the activity of HUWE1 underlies conformational control in response to physiological cues—a mechanism that may be exploited for cancer therapy.
KW  - Medicine
KW  - Structural Biology
KW  - Molecular Biophysics
KW  - HUWE1
KW  - HECT Ligase
KW  - Ubiquitin
KW  - P14ARF
KW  - X-Ray Chrystallography
KW  - Enzyme Regulation
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171862
VL  - 6
ER  - 
TY  - JOUR
A1  - Mieczkowski, Mateusz
A1  - Steinmetzger, Christian
A1  - Bessi, Irene
A1  - Lenz, Ann-Kathrin
A1  - Schmiedel, Alexander
A1  - Holzapfel, Marco
A1  - Lambert, Christoph
A1  - Pena, Vladimir
A1  - Höbartner, Claudia
T1  - Large Stokes shift fluorescence activation in an RNA aptamer by intermolecular proton transfer to guanine
JF  - Nature Communications
N2  - Fluorogenic RNA aptamers are synthetic functional RNAs that specifically bind and activate conditional fluorophores. The Chili RNA aptamer mimics large Stokes shift fluorescent proteins and exhibits high affinity for 3,5-dimethoxy-4-hydroxybenzylidene imidazolone (DMHBI) derivatives to elicit green or red fluorescence emission. Here, we elucidate the structural and mechanistic basis of fluorescence activation by crystallography and time-resolved optical spectroscopy. Two co-crystal structures of the Chili RNA with positively charged DMHBO+ and DMHBI+ ligands revealed a G-quadruplex and a trans-sugar-sugar edge G:G base pair that immobilize the ligand by π-π stacking. A Watson-Crick G:C base pair in the fluorophore binding site establishes a short hydrogen bond between the N7 of guanine and the phenolic OH of the ligand. Ultrafast excited state proton transfer (ESPT) from the neutral chromophore to the RNA was found with a time constant of 130 fs and revealed the mode of action of the large Stokes shift fluorogenic RNA aptamer.
KW  - Fluorogenic RNA Aptamers
KW  - Synthetic Functional RNAs
KW  - Chili RNA Aptamer
KW  - Co-Crystal Structures of Chili RNA
KW  - RNA
KW  - Optical Spectroscopy
KW  - Structural Biology
KW  - X-ray Crystallography
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-254527
VL  - 12
ER  -