Holub M, Birnie A, Japaridze A, van der Torre J, Ridder MD, de Ram C, Pabst M, Dekker C. Extracting and characterizing protein-free megabase-pair DNA for
in vitro experiments.
CELL REPORTS METHODS 2022;
2:100366. [PMID:
36590691 PMCID:
PMC9795359 DOI:
10.1016/j.crmeth.2022.100366]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 09/29/2022] [Accepted: 11/16/2022] [Indexed: 12/15/2022]
Abstract
Chromosome structure and function is studied using various cell-based methods as well as with a range of in vitro single-molecule techniques on short DNA substrates. Here, we present a method to obtain megabase-pair-length deproteinated DNA for in vitro studies. We isolated chromosomes from bacterial cells and enzymatically digested the native proteins. Mass spectrometry indicated that 97%-100% of DNA-binding proteins are removed from the sample. Fluorescence microscopy analysis showed an increase in the radius of gyration of the DNA polymers, while the DNA length remained megabase-pair sized. In proof-of-concept experiments using these deproteinated long DNA molecules, we observed DNA compaction upon adding the DNA-binding protein Fis or PEG crowding agents and showed that it is possible to track the motion of a fluorescently labeled DNA locus. These results indicate the practical feasibility of a "genome-in-a-box" approach to study chromosome organization from the bottom up.
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