Biology subjects

Hollmann, N. M.

Publications and source records attributed to Hollmann, N. M..

4 recordsLinked to original sources

bioRxiv2026

Structural Basis for Dimeric Genome Selection by HIV-1

HIV-1 packages a dimeric RNA genome into assembling virions, a requirement for replication. To understand the mechanism of dimer selection, we conducted cryogenic electron microscopy (cryoEM) studies of nascent assemblies formed between HIV-1 Gag protein constructs and genomic RNA elements that promote dimerization and packaging. CryoEM maps revealed structural architectures in which the helical dimer initiation signal (DIS) of the RNA packaging signal bridges two 6-helix bundles (6HBs) that protrude from adjacent Gag hexamers. Conserved guanosines that sandwich the DIS are located beneath the 6HBs and poised to interact with clusters of nucleocapsid domains. Mutation of these guanosines severely impairs RNA packaging into virus-like particles. Our findings suggest that DIS functions as a molecular ruler, organizing Gag hexamers into structures optimized for Gag lattice expansion.

molecular biology↗

bioRxiv2023

The Listeria monocytogenes persistence factor ClpL is a potent stand-alone disaggregase

Heat stress can cause cell death by triggering the aggregation of essential proteins. In bacteria, aggregated proteins are rescued by the canonical Hsp70/AAA+ (ClpB) bi-chaperone disaggregase. Man-made, severe stress conditions applied during e.g. food-processing represent a novel threat for bacteria by exceeding the capacity of the Hsp70/ClpB system. Here, we report on the potent autonomous AAA+ disaggregase ClpL from Listeria monocytogenes that provides enhanced heat resistance to the food-borne pathogen enabling persistence in adverse environments. ClpL shows increased thermal stability and enhanced disaggregation power compared to Hsp70/ClpB, enabling it to withstand severe heat stress and to solubilize tight aggregates. ClpL binds to protein aggregates via aromatic residues present in its N-terminal domain (NTD) that adopts a partially folded and dynamic conformation. Target specificity is achieved by simultaneous interactions of multiple NTDs with the aggregate surface. ClpL shows remarkable structural plasticity by forming diverse higher assembly states through interacting ClpL rings. NTDs become largely sequestered upon ClpL ring interactions. Stabilizing ring assemblies by engineered disulfide bonds strongly reduces disaggregation activity, suggesting that they represent storage states.

biochemistry↗

bioRxiv2022

Upstream of N-Ras C-terminal cold shock domains mediate poly(A) specificity in a novel RNA recognition mode and bind poly(A) binding protein during translation regulation

RNA binding proteins (RBPs) often engage multiple RNA binding domains (RBDs) to increase target specificity and affinity. However, the complexity of target recognition of multiple RBDs remains largely unexplored. Here we use Upstream of N-Ras (Unr), a multidomain RBP, to demonstrate how multiple RBDs orchestrate target specificity. A crystal structure of the three C-terminal RNA binding cold-shock domains (CSD) of Unr bound to a poly(A) sequence exemplifies how recognition goes beyond the classical {pi}-{pi}-stacking in CSDs. Further structural studies reveal several interaction surfaces between the N-terminal and C-terminal part of Unr with the poly(A)-binding protein (pAbp). This provides first atomistic details towards understanding regulation of translation initiation that is mediated by the interplay of these two proteins with each other and RNA.

molecular biology↗

bioRxiv2018

Structure, dynamics and roX2-lncRNA binding of tandem double-stranded RNA binding domains dsRBD1,2 of Drosophila helicase Maleless

Maleless (MLE) is an evolutionary conserved member of the DExH family of helicases in Drosophila. Besides its function in RNA editing and presumably siRNA processing, MLE is best known for its role in remodelling non-coding roX RNA in the context of X chromosome dosage compensation in male flies. MLE and its human orthologue, DHX9 contain two tandem double-stranded RNA binding domains (dsRBDs) located at the N-terminal region. The two dsRBDs are essential for localization of MLE at the X-territory and it is presumed that this involves binding roX secondary structures. However, for dsRBD1 roX RNA binding has so far not been described. Here, we determined the solution NMR structure of dsRBD1 and dsRBD2 of MLE in tandem and investigated its role in double-stranded RNA (dsRNA) binding. Our NMR data show that both dsRBDs act as independent structural modules in solution and are canonical, non-sequence-specific dsRBDs featuring non-canonical KKxAK RNA binding motifs. NMR titrations combined with filter binding experiments document the contribution of dsRBD1 to dsRNA binding in vitro. Curiously, dsRBD1 mutants in which dsRNA binding in vitro is strongly compromised do not affect roX2 RNA binding and MLE localization in cells. These data suggest alternative functions for dsRBD1 in vivo.

biochemistry↗