Biology subjects

Avidan, N.

Publications and source records attributed to Avidan, N..

5 recordsLinked to original sources

bioRxiv2024

Autonomous biogenesis of the entire protein translation machinery excluding ribosomes

Recreating the conditions for autonomous biogenesis of the protein translation machinery is fundamental to our understanding of living systems and is essential for the assembly of minimal cell models. All components of the translation machinery, including the ribosomes, translation factors and aminoacyl tRNA synthetases, are made of proteins and are therefore involved in their own synthesis, posing a unique challenge for self-biogenesis. Here, we created physicochemical conditions for autonomous biogenesis of all the translation machinery, excluding the ribosome. We surface-immobilized synthetic genes coding for all thirty components as densely packed DNA brushes forming a reaction center that localizes, concentrates and catalyzes their simultaneous synthesis. To demonstrate their activity, we first determined empirically the minimal critical concentration of each translation protein required to initiate its own self-biogenesis in bulk solution. We then assembled a minimal gene expression reaction with all translation proteins at their critical concentrations. Under these dilute conditions, reporter proteins were not synthesized unless the DNA brushes encoded all the translation proteins, thereby demonstrating their co-synthesis, functionality and engagement in their own synthesis. This scenario of a complex biochemical process that amplifies itself can be generalized and extended to impact our understanding toward the design of autonomous self-replicating biological system.

synthetic biology↗

bioRxiv2024

Cell-free immuno-profiling on a genetically programmed biochip

Emerging cell-free synthetic biology approaches provide biosafe, cheap, and versatile genetic tools to advance therapeutic research and development. Combined with micro-fabrication technology, we developed a platform to quantitatively reconstitute interactions of cell-free synthesized antigens with antibodies and human receptors in miniaturized compartments on a silicon chip. Photolithographic surface patterning of protein traps and on chip expression from high density gene brushes generated a continuous surface density gradient of fluorescently labeled antigens. Antibodies binding to the antigen gradient generate a full binding curve in each single compartment for affinity determination. We used the SARS-CoV-2 antigens as a model to profile the specificity and affinity of monoclonal antibodies to > 30 viral epitopes synthesized simultaneously on one chip in a genotype-phenotype linked compartments. We further profiled polyclonal antibodies in minute volumes of human sera, revealing patient-specific epitope profiles that are difficult to detect by conventional approaches. Cell-free co-synthesis of the human ACE2 receptor with the viral Receptor-Binding-Domain yielded relative binding affinities to different SARS-CoV-2 variants. This rapid, quantitative, and on-chip genetically programmed approach allows to study complex protein-protein interactions independent of protein purification steps for human immuno-profiling with a fast response time for combating emerging pathogens.

bioengineering↗

bioRxiv2024

Fast Low-Input Efficient Hi-C

We developed FLIE (Fast Low-Input Efficient) Hi-C, a highly optimized and simplified version of Hi-C. Our method shortens the duration of Hi-C from five days to two days and decreases key reagent amounts 5-20 fold, while maintaining experimental controls and data quality. Importantly, the method also reduces the required input material by 100-1000 fold, as we demonstrate by generating detailed high complexity interaction maps from low-input sorted mouse frozen neuron nuclei and from 5,000-10,000 human Hap1 cells.

genomics↗

bioRxiv2024

Large-scale manipulation of radial positioning does not affect most aspects of genome organization

Although the spatial organization of the genome is closely linked to biological function, genome structure is highly stochastic. Within this heterogeneity, specific function-associated structural elements must be maintained, even when the nucleus is deformed due to physiological physical constraints. The radial positioning of genomic loci - their distance from the nuclear periphery - has long been considered an important feature of genome organization which is correlated with both structural elements and genomic activity. In the current study, we developed an experimental system for manipulating the radial positioning of the genome, by expressing the sperm-specific protein Prm1 in somatic cells. By microscopy, we observe that initial Prm1 nuclear foci develop within 72 hours into a large Prm1 focus occupying most of the nuclear interior, while the entire genome is driven towards the nuclear periphery, resulting in a 3-5 fold reduction in the volume that the genome occupies. Noting that this system enables isolation of a pure population of cells with reorganized nuclei, we then used Hi-C to study the effects of this perturbation. Remarkably, we find that interaction patterns are largely robust to this major nuclear reorganization, with minor changes which mostly reflect a strengthening of heterochromatin self-interactions. Our experimental system provides means for manipulating nuclear organization in a reproducible manner, potentially allowing to examine radial positioning decoupled from other features of genome organization. Highlighting the complementary nature of microscopic and genomic methods, our work further suggests a remarkable resilience of genome structure such that large-scale nuclear changes, including chromosome compression and changes in radial positioning, can occur without extensive alteration of functional genome organization.

genomics↗

bioRxiv2022

Recruitment of transcriptional effectors by Cas9 creates cis regulatory elements and demonstrates distance-dependent transcriptional regulation

It is essential to regulate the expression of genes, such as those encoding the proteins of the cardiac sarcomere. This regulation is often mediated by cis regulatory elements termed enhancers and repressors that recruit transcription factors to gene-distal sites. However, the relationship between transcription factors recruitment to gene-distant sites and the regulation of gene expression is not fully understood. Specifically, it is unclear if such recruitment to any genomic site is sufficient to form an enhancer or repressor at the site, and what is the relationship between the cis regulatory elements position and its ability to control the transcription of distant genes. Using dead Cas9 to recruit either viral or endogenous transcription factor activation domains, we demonstrate that targeting naive genomic sites lacking open chromatin or active enhancer marks is sufficient to alter the chromatin signature of the target site, the distant gene promoter, and significantly induce the distant gene expression, even across chromatin insulating loci. The magnitude of induction is affected by the distance between the activation site and the cognate gene in a non-linear manner. Dead Cas9 mediated recruitment of repression domains behave similarly to activation in that targeting of non-regulatory regions could repress gene expression with a nonlinear distance dependence and across chromatin insulating loci. These findings expand the models of enhancer generation and function by showing that an arbitrary genomic site can become a regulatory element and interact epigenetically and transcriptionally with a distant promoter. They also provide new fundamental insights into the rules governing gene expression.

genomics↗