Nuclear peripheral chromatin-lamin B1 interaction is required for global integrity of chromatin architecture and dynamics in human cells

The eukaryotic genome is folded into higher-order conformation accompanied with constrained dynamics for coordinated genome functions.However,the molecular machinery underlying these hierarchically organized three-dimensional(3D)chromatin architecture and dynamics remains poorly understood.Here by combining imaging and sequencing,we studied the role of lamin B1 in chromatin architecture and dynamics.We found that lamin B1 depletion leads to detachment of lamina-associated domains(LADs)from the nuclear periphery accompanied with global chromatin redistribution and decompaction.Consequently,the interchromosomal as well as inter-compartment interactions are increased,but the structure of topologically associating domains(TADs)is not affected.Using live-cell genomic loci tracking,we further proved that depletion of lamin B1 leads to increased chromatin dynamics,owing to chromatin decompaction and redistribution toward nucleoplasm.Taken together,our data suggest that lamin B1 and chromatin interactions at the nuclear periphery promote LAD maintenance,chromatin compaction,genomic compartmentalization into chromosome territories and A/B compartments and confine chromatin dynamics,supporting their crucial roles in chromatin higher-order structure and chromatin dynamics.

Illuminating the structure and dynamics of chromatin by fluorescence labeling

BACKGROUND： Visualization of chromosomal loci location and dynamics is crucial for understanding many fundamental intra-nuclear processes such as DNA transcription, replication, and repair. OBJECTIVE： Here, we will describe the development of fluorescence labeling methods for chromatin imaging, including traditional as well as emerging chromatin labeling techniques in both fixed and live cells. We will also discuss current issues and provide a perspective on future developments and applications of the chromatin labeling technology. METHODS： A systematic literature search was performed using the PubMed. Studies published over the past 50 years were considered for review. More than 100 articles were cited in this review. RESULTS： Taking into account sensitivity, specificity, and spatiotemporal resolution, fluorescence labeling and imaging has been the most prevalent approach for chromatin visualization. Among all the fluorescent labeling tools, the adoption ofgenome editing tools, such as TALE and CRISPR, have great potential for the labeling and imaging of chromatin. CONCLUSION： Although a number of chromatin labeling techniques are available for both fixed and live cells, much more effort is still clearly required to develop fluorescence labeling methods capable of targeting arbitrary sequences non-intrusively to allow long-term, multiplexing, and high-throughput imaging of genomic loci and chromatin structures. The emerging technological advances will outline a next-generation effort toward the comprehensive delineation of chromatin at single-cell level with single-molecule resolution.