Because of their pervasiveness in eukaryotic genomes and their unique properties, understanding the role that ID (intrinsically disordered) regions in proteins play in the interactome is essential for gaining a better understanding of the network. Especially critical in determining this role is their ability to bind more than one partner using the same region. Studies have revealed that proteins containing ID regions tend to take a central role in protein interaction networks; specifically, they act as hubs, interacting with multiple different partners across time and space, allowing for the co-ordination of many cellular activities. There appear to be three different modules within ID regions responsible for their functionally promiscuous behaviour: MoRFs (molecular recognition features), SLiMs (small linear motifs) and LCRs (low complexity regions). These regions allow for functionality such as engaging in the formation of dynamic heteromeric structures which can serve to increase local activity of an enzyme or store a collection of functionally related molecules for later use. However, the use of promiscuity does not come without a cost: a number of diseases that have been associated with ID-containing proteins seem to be caused by undesirable interactions occurring upon altered expression of the ID-containing protein. The paper can be found here.
The proper functional development of a multicellular organism depends on an intricate network of interacting genes that are expressed in accurate temporal and spatial patterns across different tissues. Complex inhibitory and excitatory interactions among genes control the territorial differences that explain specialized cell fates, embryo polarization and tissues architecture in metazoans. Given the nature of the regulatory gene networks, similarity of expression patterns can identify genes with similar roles. The inference and analysis of the gene interaction networks through complex network tools can reveal important aspects of the biological system modeled. Here we suggest an image analysis pipeline to quantify co-localization patterns in in situ hybridization images of Drosophila embryos and, based on these patterns, infer gene networks. We analyze the spatial dispersion of the gene expression and show the gene interaction networks for different developmental stages. Our results suggest that the inference of developmental networks based on spatial expression data is biologically relevant and represents a potential tool for the understanding of animal development. The paper can be found here.
Alternatively spliced protein segments tend to be intrinsically disordered and contain linear interaction motifs and/or post-translational modification sites. An emerging concept is that differential inclusion of such disordered segments can mediate new protein interactions, and hence change the context in which the biochemical or molecular functions are carried out by the protein. Since genes with disordered regions are enriched in regulatory and signaling functions, the resulting protein isoforms could alter their function in different tissues and organisms by rewiring interaction networks through the recruitment of distinct interaction partners via the alternatively spliced disordered segments. In this manner, the alternative splicing of mRNA coding for disordered segments may contribute to the emergence of new traits during evolution, development and disease. The paper by Marija Buljan et al can be found here.
In this work, we objectively compare known structures and reveal key similarities and differences among diverse GPCRs. We identify a consensus structural scaffold of GPCRs that is constituted by a network of non-covalent contacts between residues on the transmembrane helices. By systematically analysing structures of the different receptor–ligand complexes, we identify a consensus ‘ligand-binding cradle’ that constitutes the bottom of the ligand-binding pocket within the TM bundle. Furthermore, our comparative study suggests that the third TM helix has a central role as a structural and functional hub. The paper can be found here and the press release by MRC can be found here. Our work was No. 1 in Nature’s top 10 downloaded articles in February 2013, featured in Nature’s GPCR focus section and mentioned in the cover page.
In this paper, we present a general statistical framework that is widely applicable to the analysis of genomic contact maps, irrespective of the data acquisition and normalization processes. Within this framework DNA–DNA contact data are represented as a complex network where DNA segments and contacts between them are denoted as nodes and edges, respectively. We also present a robust method for generating randomized contact networks that explicitly take into account the inherent 3D nature of the genome and serve as realistic null-models for unbiased statistical analyses. Our paper was chosen as a featured article by NAR. The paper by Kai Kruse et al can be found here.
Growing evidence suggests that aggregation-prone proteins are both harmful and functional for a cell. How do cellular systems balance the detrimental and beneficial effect of protein aggregation? In this work, we reveal that aggregation-prone proteins are subject to differential transcriptional, translational, and degradation control compared to nonaggregation-prone proteins, which leads to their decreased synthesis, low abundance, and high turnover. Genetic modulators that enhance the aggregation phenotype are enriched in genes that influence expression homeostasis. Moreover, genes encoding aggregation-prone proteins are more likely to be harmful when overexpressed. The trends are evolutionarily conserved and suggest a strategy whereby cellular mechanisms specifically modulate the availability of aggregation-prone proteins to (1) keep concentrations below the critical ones required for aggregation and (2) shift the equilibrium between the monomeric and oligomeric/aggregate form, as explained by Le Chatelier’s principle. This strategy may prevent formation of undesirable aggregates and keep functional assemblies/aggregates under control. The paper can be found here.
In this perspective piece, we discuss the notion that disordered regions are largely passive is being actively challenged by the idea that they perform diverse functions. We also discuss how the synergy between structured and disordered regions expands the functional repertoires of proteins. You can read the Perspective here and an accompanying news article here.
Dr. Balaji Santhanam from Harvard University has just started as a new Senior Investigator Scientist at the LMB. A very warm welcome from all of us Balaji. We are looking forward to some very exciting discussions and science in the coming days.
Elisabetta and James are our two new summer students who started this month. A very warm welcome to both of you and we look forward to some exciting science in the next couple of months!
AJ Venkatakrishnan and Natalia de Groot have been awarded the MRC Centenary Award to pursue their research on protein structure networks and protein aggregation. Many congratulations to them!