Biology subjects

Hansen, A. L.

Publications and source records attributed to Hansen, A. L..

3 recordsLinked to original sources

bioRxiv2023

Thermodynamic Coupling of the tandem RRM domains of hnRNP A1 underlie its Pleiotropic RNA Binding Functions

The functional properties of RNA-binding proteins (RBPs) require allosteric regulation through inter-domain communication. Despite the foundational importance of allostery to biological regulation, almost no studies have been conducted to describe the biophysical nature by which inter-domain communication manifests in RBPs. Here, we show through high-pressure studies with hnRNP A1 that inter-domain communication is vital for the unique stability of its N- terminal domain containing a tandem of RNA Recognition Motifs (RRMs). Despite high sequence similarity and nearly identical tertiary structures, the two RRMs exhibit drastically different stability under pressure. RRM2 unfolds completely under high-pressure as an individual domain, but when appended to RRM1, it remains stable. Variants in which inter-domain communication is disrupted between the tandem RRMs show a large decrease in stability under pressure. Carrying these mutations over to the full-length protein for in vivo experiments revealed that the mutations affected the ability of the disordered C-terminus to engage in protein-protein interactions and more importantly, they also influenced the RNA binding capacity. Collectively, this work reveals that thermodynamic coupling between the tandem RRMs of hnRNP A1 accounts for its allosteric regulatory functions.

biochemistry↗

bioRxiv2023

Phosphorylation modulates estrogen receptor disorder by altering long-range hydrophobic interactions

Protein intrinsic disorder is coupled to a range of biological phenomena, from gene regulation to cancer progression. Phosphorylation of the estrogen receptor (ER) at Ser118 through its disordered N-terminal domain (NTD) activates its transcriptional function, but it is challenging to rationalize how this modification regulates ER activity. Using biophysical approaches of small-angle X-ray scattering and nuclear magnetic resonance spectroscopy, we demonstrate that Ser118 phosphorylation triggers long-range conformational changes in ER-NTD, particularly between two hydrophobic clusters of residual structures. Alanine substitution of hydrophobic amino acids near Ser118 produces similar conformational alterations and rescues impaired ER activity caused by a phosphorylation-deficient mutant. These findings establish a direct link between phosphorylation-induced conformational changes and the activation function of this disordered protein as a promising avenue to block ER transcriptional activation.

biophysics↗

bioRxiv2021

Towards the NMR solution Structure and the Dynamics of the C-terminal Region of APOL1 and its G1, G2 Variants with a Membrane Mimetic

Secreted apolipoprotein L1 (APOL1) is well known as an innate immune factor, protecting against African trypanosomiasis. The intracellular form has multiple functions, including regulating autophagy, intracellular vesicle trafficking, and ion channel activity. The APOL1 protein (G0) has two common variants (denoted G1 and G2) in the C-terminal region and are associated with a high risk of chronic kidney disease (CKD) and progression to end-stage kidney disease. Our previous studies using molecular modeling suggested that APOL1 G1 and G2 stabilize an autoinhibited state of the C-terminus, leading to impaired intracellular interactions with SNARE proteins. To characterize the structural consequence of kidney disease-associated APOL1 variants further, we assigned the C-terminal region proteins using 1H, 13C, 15N multidimensional nuclear magnetic resonance (NMR) spectra in solution in the presence of membrane mimetic dodecylphosphocholine micelles. We then derived models for the three-dimensional structure of APOL1-G0, and -G1 and -G2 variant C-terminal regions using the chemical shifts of the main chain nuclei followed by NMR relaxation measurements. The data suggest that changes in the three-dimensional structure of APOL1 C-terminal region induced by kidney disease-associated variants, not least the alteration of key sidechains and their interactions, could disrupt membrane association and the yet to be characterized protein-protein interactions including its binding partners, such as SNARE proteins. Such interactions could underlie the intracellular mechanisms that mediate the pathogenesis of CKD. In the future, one may try to reverse such structural and dynamics changes in the protein by designing agents that may bind and then mitigate APOL1 variant-associated CKD.

biophysics↗