ABSTRACT
The three-dimensional (3D) genome organization plays an important role in gene regulation. As a basic functional unit of the genome, topologically associated domain (TAD) regulates multiplebiological processes such as gene expression and DNA replication and plays a role in radiation-inducedDNA damage repair. Recent studies showed that TAD is not a completely independent domain butcontains hierarchical internal domains, which could be a new mechanism of gene regulation. To explorethe role of hierarchical TAD in cellular responses to radiation, we apply the OnTAD algorithm, anoptimized nested TAD caller from Hi-C data, to identify hierarchical TAD in 26 Hi-C data from Geneexpression omnibus (GEO) database. These data were from irradiated fibroblasts, lymphoblasts andfibroblasts deficient in the ataxia telangiectasia mutated (ATM) gene with 5 Gy X-ray. We observe thatX-ray can regularly affect the hierarchy of TAD in which high-level TAD is prone to change and low-levelTAD is more conservative. We propose that radiation-induced TAD hierarchy change can regulate cellularresponses to radiation by regulating gene expression, and ATM is a necessary factor for radiation-inducedTAD hierarchy change and recovery. This study provides new insights into the role of the 3D genome inradiation-induced cellular responses from the perspective of hierarchical TAD structures.
ABSTRACT
Interactions between chromatin segments play a large role in functional genomic assays and developments in genomic interaction detection methods have shown interacting topological domains within the genome. Among these methods, Hi-C plays a key role. Here, we present the Genome Interaction Tools and Resources (GITAR), a software to perform a comprehensive Hi-C data analysis, including data preprocessing, normalization, and visualization, as well as analysis of topologically-associated domains (TADs). GITAR is composed of two main modules: (1) HiCtool, a Python library to process and visualize Hi-C data, including TAD analysis; and (2) processed data library, a large collection of human and mouse datasets processed using HiCtool. HiCtool leads the user step-by-step through a pipeline, which goes from the raw Hi-C data to the computation, visualization, and optimized storage of intra-chromosomal contact matrices and TAD coordinates. A large collection of standardized processed data allows the users to compare different datasets in a consistent way, while saving time to obtain data for visualization or additional analyses. More importantly, GITAR enables users without any programming or bioinformatic expertise to work with Hi-C data. GITAR is publicly available at http://genomegitar.org as an open-source software.
Subject(s)
Animals , Humans , Mice , Chromatin , Chemistry , Computer Graphics , Genome , Genomics , Methods , SoftwareABSTRACT
It is becoming increasingly clear that eukaryotic genomes are subjected to higher-order chromatin organization by the CCCTC-binding factor/cohesin complex. Their dynamic interactions in three dimensions within the nucleus regulate gene transcription by changing the chromatin architecture. Such spatial genomic organization is functionally important for the spatial disposition of chromosomes to control cell fate during development and differentiation. Thus, the dysregulation of proper long-range chromatin interactions may influence the development of tumorigenesis and cancer progression.