Final answer:
Negative supercoiling in nucleosomes occurs as DNA wraps around histone proteins, causing underwinding and corresponding opposite twists in the DNA structure. This process is dynamic and influenced by ATP-dependent remodeling complexes that can alter nucleosome spacing.
Step-by-step explanation:
How do nucleosomes incur negative supercoiling? DNA wrapped around histone proteins forms nucleosomes, giving rise to a "beads on a string" structure. These nucleosomes can slide along the DNA, impacting the density of the packing and hence the access to the DNA for transcription factors and other proteins. Highly basic and positively charged histone proteins interact with the negatively charged DNA. ATP-dependent remodeling complexes can reposition nucleosomes, altering their spacing. Condensation into the 30 nm chromatin fiber and further condensation during mitosis indicates additional levels of structure and control, which can lead to the induction of negative supercoiling. Negative supercoiling occurs as a response to the underwinding of DNA that takes place when it wraps around nucleosomes, causing the DNA to twist in the opposite direction of the helical twist.