The first 20 amino acids of cyclin B1 can promote association with mitotic chromosomes.

<p><b>A</b>. Representative images of mitotic BS-C-1 cells expressing GFP fusions of WT^1–433 cyclin B1, GFP only, or fragments of cyclin B1 that lack the C-terminus. The GFP signal is detected by the FITC channel (top) and the position of the metaphase plate (indicated with white arrows) can be identified with DIC optics (bottom). Scale bar = 10 µm. <b>B</b>. Box-and-whisker plots of Chromosome Enrichment Ratios (CER) for the constructs shown in part A. The CER is calculated as the ratio of the mean fluorescence intensity of the chromosomal region to the mean fluorescence intensity of the entire cell. The diamond indicates the mean CER. The box represents the 2^nd and 3^rd quartiles of the data, with the horizontal line representing the median and the whiskers representing the range. The red dotted line indicates the threshold of 1.6 that correlates with chromosome association in the qualitative assay. N = 8–14, ** indicates p < 0.01 and *** indicates p<0.001 compared to WT^1–433. Further details including mean CER, standard deviations, and Wilcoxon exact test p-values can be found in Table S2. <b>C</b>. Representative mitotic BS-C-1 cells expressing GFP fusions of cyclin B1 fragments that lack different regions of the N- and C-termini. The metaphase plate is indicated by white arrows. Scale bar = 10 µm. <b>D</b> CER plots for the constructs shown in part C. The red dotted line indicates the threshold of 1.6. N = 10–11, *** indicates p<0.001 compared to the WT^1–433, WT^1–166, WT^1–110, respectively. Further details including mean CER, standard deviations, and Wilcoxon exact test p-values can be found in Table S2.