Here, we developed the CRdb database (http://cr.liclab.net/crdb), which aimed to record a large number of available resources for CRs, and provided extensive annotations and analysis of CRs.

The current version of CRdb collected a total of 647 CRs and 2,591 CRs associated ChIP-seq data from more than 300 human tissues and cell types. These samples have been manually curated from NCBI GEO/SRA and ENCODE. CRdb emphatically provided the circumstantial and numerous (epi) genetic annotations in CR-binding regions by processing and integrating large-scale high/low-throughput experimental data, including super-enhancers, enhancers, transcription factor binding sites (TFBS), methylation sites, common single nucleotide polymorphisms (SNPs), risk SNPs, expression quantitative trait locus (eQTL), 3D chromatin interactions and accessible chromatin. CRdb also provided CR downstream target genes via five methods. Furthermore, CRdb supported upstream regulatory information and various functional annotations of CRs, including Gene Ontology (GO) terms, pathways, protein-protein interactions (PPIs), cancer hallmarks, survival, disease information and gene expression. In particular, CRdb embedded four types of CR regulatory analyses for users, including CR gene set enrichment, CR binding genomic region annotation, CR-TF co-occupancy analysis and CR regulatory axis analysis. CRdb can become a serviceable and powerful platform to explore the underlying functions and regulatory mechanisms of CRs in diseases and biological processes.