Figure 3.

Mobility of BRCA2 fusion proteins determined by FCS. (A) Autocorrelation curves C(τ) were fitted with a three-component model, for ES cells with homozygous BRCA2-GFP and BRCA2-YFP knock-ins and for ES cells transiently expressing GFP and YFP, as indicated by color. Raw and fitted data are shown as solid and broken lines, respectively. ACF curves were postnormalized between 1 and 2 for better comparison of the diffusion characteristics, but the residuals were left unchanged. (B) The intensity fluctuation raw data and the photon counting histograms are displayed for cells transiently expressing GFP at a low concentration and Brca2-GFP homozygous knock-in cells, using an integration time of 4 ms. Although the photon counting histogram for GFP-expressing cells is symmetric, the histogram for BRCA2-GFP is skewed, suggesting a heterogeneous BRCA2-GFP population consisting of BRCA2 oligomers with varying protein number. The data shown are representative of multiple experimental repeats (n = 10 cells).