Journal
MOLECULAR BIOLOGY OF THE CELL
Volume 23, Issue 24, Pages 4864-4871Publisher
AMER SOC CELL BIOLOGY
DOI: 10.1091/mbc.E12-07-0518
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Funding
- National Science Foundation [DMR-0715099, PHY-0852130, DMR-0520513, MCB-1022117, DMR-1206868]
- National Institutes of Health [U54CA143869-01, GM057839]
- Chicago Biomedical Consortium
- Searle Funds at the Chicago Community Trust
- Direct For Biological Sciences
- Div Of Molecular and Cellular Bioscience [1022117] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1206868] Funding Source: National Science Foundation
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Histone H1 binds to linker DNA between nucleosomes, but the dynamics and biological ramifications of this interaction remain poorly understood. We performed single-molecule experiments using magnetic tweezers to determine the effects of H1 on naked DNA in buffer or during chromatin assembly in Xenopus egg extracts. In buffer, nanomolar concentrations of H1 induce bending and looping of naked DNA at stretching forces below 0.6 pN, effects that can be reversed with 2.7-pN force or in 200 mM monovalent salt concentrations. Consecutive tens-of-nanometer bending events suggest that H1 binds to naked DNA in buffer at high stoichiometries. In egg extracts, single DNA molecules assemble into nucleosomes and undergo rapid compaction. Histone H1 at endogenous physiological concentrations increases the DNA compaction rate during chromatin assembly under 2-pN force and decreases it during disassembly under 5-pN force. In egg cytoplasm, histone H1 protects sperm nuclei undergoing genome-wide decondensation and chromatin assembly from becoming abnormally stretched or fragmented due to astral microtubule pulling forces. These results reveal functional ramifications of H1 binding to DNA at the single-molecule level and suggest an important physiological role for H1 in compacting DNA under force and during chromatin assembly.
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