DSB

DSB
Name	DSB
Othernames	Double-strand break
Field	Molecular biology, Genetics, Medicine

DSB DSB is a molecular lesion characterized by the discontinuity of both strands of a DNA duplex. It is a focal concept in studies of James Watson-era DNA replication research, Hermann Muller mutagenesis experiments, and modern investigations at institutions like the Cold Spring Harbor Laboratory, Max Planck Institute, and National Institutes of Health. DSBs are central to understanding processes studied by investigators at the European Molecular Biology Laboratory, Broad Institute, Whitehead Institute, and clinical centers such as Mayo Clinic and Johns Hopkins Hospital.

Definition and Nomenclature

DSB denotes a break in both complementary strands of a DNA molecule, distinct from single-strand lesions characterized in early work by Avery–MacLeod–McCarty-era bacteriology and later by Linus Pauling studies. Terminology evolved through reports from Hermann Muller on X-ray mutagenesis and Barbara McClintock on chromosome breakage, entering standardized vocabularies used at the International Union of Biochemistry and Molecular Biology and committees at the World Health Organization. Synonyms appear in literature from the Royal Society and journals like Nature and Science, and nomenclature aligns with classification schemes adopted by the Human Genome Project and panels at the National Academy of Sciences.

Biological Roles and Mechanisms

DSBs arise in physiological contexts such as immunoglobulin class switch recombination studied at National Institutes of Allergy and Infectious Diseases, meiotic recombination orchestrated by proteins characterized in labs of H. Robert Horvitz and Elizabeth Blackburn, and programmed genome rearrangements in ciliates investigated by groups at MIT and University of Cambridge. Mechanistically, DSBs can result from replication fork collapse described by researchers at Princeton University and Stanford University, topoisomerase II failure reported in studies from Harvard Medical School, and reactive oxygen species processes examined by teams at University of Oxford. Key enzymatic actors implicated include complexes analogous to observations in studies of Spo11 in meiosis, RAG1/RAG2 in lymphocyte development, and Topoisomerase II in mitotic segregation.

Detection and Measurement Techniques

Detection methods for DSBs were refined in protocols disseminated by groups at Cold Spring Harbor Laboratory and in methodological papers in Cell and EMBO Journal. Common assays include pulsed-field gel electrophoresis developed alongside work at University of Wisconsin–Madison, neutral comet assays popularized by laboratories at University of Birmingham, immunofluorescence microscopy using markers such as phosphorylated histone variants described by investigators at Dana-Farber Cancer Institute, and next-generation sequencing approaches pioneered at the Broad Institute. Quantitation tools integrate flow cytometry instrumentation available from companies collaborating with Massachusetts Institute of Technology researchers and bioinformatics pipelines first implemented in projects like the ENCODE Project.

Cellular Responses and Repair Pathways

Cells sense and signal DSBs through pathways elaborated in landmark studies by teams at Cold Spring Harbor Laboratory and Rockefeller University. Sensor and mediator proteins identified include kinases analogous to discoveries in papers from Yale University and University of California, San Francisco; downstream effectors coordinate cell-cycle checkpoints studied in work at Imperial College London and Karolinska Institute. Principal repair pathways include non-homologous end joining characterized in experiments at University of Chicago, homologous recombination elucidated in studies from University of Cambridge and Max Planck Institute for Biochemistry, and alternative end-joining pathways reported by groups at McGill University. Repair fidelity and pathway choice influence chromosomal translocations documented in clinical cytogenetics units at Memorial Sloan Kettering Cancer Center and Fred Hutchinson Cancer Center.

Clinical Significance and Disease Associations

DSBs contribute to pathologies investigated at oncology centers such as MD Anderson Cancer Center, Dana-Farber Cancer Institute, and Royal Marsden Hospital. Defects in DSB repair genes described in studies from University College London and University of Toronto underlie hereditary syndromes characterized by genomic instability, including mutations in loci analogous to findings at Addenbrooke's Hospital and Great Ormond Street Hospital. DSB accumulation is implicated in aging processes explored by researchers at Salk Institute and neurodegenerative conditions studied at Karolinska Institute. Therapeutic resistance mechanisms involving DSB repair have been reported in clinical trials coordinated by European Organisation for Research and Treatment of Cancer and National Cancer Institute cooperative groups.

Experimental and Therapeutic Applications

Controlled induction of DSBs underpins technologies developed at Broad Institute, including genome editing platforms leveraging programmable nucleases characterized in seminal papers involving Jennifer Doudna, Emmanuelle Charpentier, and groups at Zentrum für Molekulare Biologie der Universität Heidelberg. Preclinical studies by teams at Cold Spring Harbor Laboratory and Stanford University exploit DSB induction for targeted gene disruption, while radiotherapy regimens optimized at Clatterbridge Cancer Centre and Royal Marsden Hospital intentionally generate DSBs to kill tumor cells. Small-molecule inhibitors targeting DSB repair enzymes have progressed through trials managed by European Medicines Agency and Food and Drug Administration-sponsored consortia, with translational research hubs at Institute of Cancer Research and University of Pennsylvania leading biomarker development.

Category:DNA repair