Biology subjects

Meijer, A. B.

Publications and source records attributed to Meijer, A. B..

3 recordsLinked to original sources

bioRxiv2019

Flexible regions in the molecular architecture of Human fibrin clots structurally resolved by XL-MS and integrative structural modeling

Upon activation, fibrinogen forms large fibrin biopolymers that coalesce into clots that assist in wound healing. Limited insights into their molecular architecture, due to the sheer size and insoluble character of fibrin clots, have however restricted our ability to develop novel treatments for clotting diseases. The so far resolved disparate structural details did provide insights into linear elongation; however, molecular details like the C-terminal domain of the -chain, the heparin-binding domain on the {beta}-chain, and others involved in lateral aggregation are lacking. To illuminate these dark areas, we applied crosslinking mass spectrometry (XL-MS) to obtain biochemical evidence in the form of over 300 distance constraints and combined this with structural modeling. These restraints additionally define the interaction network of the clots and e.g. provide molecular details for the interaction with Human Serum Albumin (HSA). We were able to construct the models of fibrinogen (excluding two highly flexible regions) and {beta}, confirm these models with known structural arrangements and map how the structure laterally aggregates to form intricate lattices together with fibrinogen{gamma} . We validate the final model by mapping mutations leading to impaired clot formation. From a list of 22 mutations, we uncovered structural features for all, including a crucial role for {beta} Arg196 in lateral aggregation. The resulting model will be invaluable for research on dysfibrinogenemia and amyloidosis, as it provides insights into the molecular mechanisms of thrombosis and bleeding disorders related to fibrinogen variants. The structure is provided in the PDB-DEV repository.

biochemistry↗

bioRxiv2017

Csde1 binds transcripts involved in protein homeostasis and controls their expression in erythropoiesis

Expression of the RNA-binding protein Csde1 (Cold shock domain protein e1) is strongly upregulated during erythropoiesis compared to other hematopoietic lineages. In the severe congenital anemia Diamond Blackfan Anemia (DBA), however, Csde1 expression is impaired. Reduced expression of Csde1 in healthy erythroblasts impaired their proliferation and differentiation, which suggests an important role for Csde1 in erythropoiesis. To investigate the cellular pathways controlled by Csde1 in erythropoiesis, we identified the transcripts that physically associate with Csde1 in erythroid cells. These mainly encoded proteins involved in ribogenesis, mRNA translation and protein degradation, but also proteins associated with the mitochondrial respiratory chain and mitosis. Crispr/Cas9-mediated deletion of the first cold shock domain of Csde1 affected RNA expression and/or protein expression of Csde1-bound transcripts. For instance, protein expression of Pabpc1 was enhanced while Pabpc1 mRNA expression was reduced indicating more efficient translation of Pabpc1 followed by negative feedback on mRNA stability. Overall, the effect of reduced Csde1 function on mRNA stability and translation of Csde1-bound transcripts was modest. Clones with complete loss of Csde1, however, could not be generated. We suggest that Csde1 is involved in feed-back control in protein homeostasis and that it dampens stochastic changes in mRNA expression.

molecular biology↗

bioRxiv2017

Csde1 cooperates with Strap to control translation of erythroid transcripts

Erythropoiesis is regulated at many levels, including control of mRNA translation. Changing environmental conditions, such as hypoxia, or the availability of nutrients and growth factors, require a rapid response enacted by the enhanced or repressed translation of existing transcripts. Csde1 is an RNA-binding protein required for erythropoiesis and strongly upregulated in erythroblasts relative to other hematopoietic progenitors. The aim of this study is to identify the Csde1-containing protein complexes, and investigate their role in regulating the translation of Csde1-bound transcripts. We show that Strap, also called Unrip, was the protein most strongly associated with Csde1 in erythroblasts. Strap is a WD40 protein involved in signaling and RNA splicing, but its role is unknown when associated with Csde1. Reduced expression of Strap did not alter the pool of transcripts bound by Csde1. Instead, it reduced the mRNA and/or protein expression of several Csde1-bound transcript, that encode for proteins essential for translational regulation during hypoxia, such as Hmbs, eIF4g3 and Pabpc4. Also affected by Strap knockdown were Vim, a Gata-1 target crucial for erythrocyte enucleation, and Elavl1, which stabilizes Gata-1 mRNA. Thus, we found that the Csde1/Strap complex is at the crossroad of multiple pathways governing translation in erythroblasts.

molecular biology↗