Ccq1p and the Condensin Proteins Cut3p and Cut14p Prevent Telomere Entanglements in the Fission Yeast Schizosaccharomyces pombe

The Schizosaccharomyces pombe telomere-associated protein Ccq1p has previously been shown to participate in telomerase recruitment, heterochromatin formation, and suppression of checkpoint activation. Here we characterize a critical role for Ccq1p in mitotic transit. We show that mitotic cells lacking Ccq1p lose minichromosomes at high frequencies but that conditional knockdown of Ccq1p expression results in telomere bridging within one cell cycle. Elevating Ccq1p expression resolves the telomere entanglements caused by decreased Taz1p activity. Ccq1p affects telomere resolution in the absence of changes in telomere size, indicating a role for Ccq1p that is independent of telomere length regulation. Using affinity purification, we identify the condensin proteins Cut3p and Cut14p as candidate Ccq1p interactors in this activity. Condensin loss-of-function disrupts Ccq1p telomeric localization and normal intertelomere clustering, while condensin overexpression relieves the chromosome segregation defects associated with conditional Ccq1p knockdown. These data suggest that Ccq1p and condensins collaborate to mediate resolution of telomeres in mitosis and regulate intertelomeric clustering during interphase.