In vivo Study of the Histone Chaperone Activity of Nucleolin by FRAP

Table 1

Summary of the FRAP results obtained for recovery rates and dissociation constants (𝐾_𝑜𝑓𝑓) extracted from Figures 2–5 for H2B, H4, and MacroH2A. The analysis was subdivided into 3 categories: control cells (in italic), silenced cells (bold), and comparison between silenced cells and control cells (italic-bold). In addition to the 2 parameters directly extracted from the results, implication of a third parameter was obvious to explain the observed recovery rates, the number of bleached histone molecules disassembled.

	H2B	H4	MacroH2A
Relative recovery rate at 1h30 in control cells	faster (37%)	slower, but variable (24%)	slower (27%)
Relative Koff in control cells	medium	faster	slower
Implication for the number of bleached histone molecules disassembled in control cells	higher number compared to H4	lower number compared to macroH2A	compatible with same number for H2B
Recovery rate in silenced nucleolin cells at 1h30	faster	slower, but variable	faster
Koff in silenced nucleolin cells compared to control cells	slower	slower in any case	faster
Implication for the number of bleached histone molecules disassembled in silenced cells	higher number compared to H4	smaller number compared to macroH2A	higher number compared to H2B
Recovery rate in silenced nucleolin cells compared to control cells	faster	identical  when splitted into a fast and a slow population	faster
Koffin silenced nucleolin cells compared to control cells	slower	slower in any case	identical
Implication for the number of bleached histone molecules disassembled in silenced cells	higher number compared to control	higher number compared to control	higher number compared to control