Bez, C.; (2012) The role of the telomere bouquet in controlling spindle pole body composition in fission yeast meiosis. Doctoral thesis , UCL (University College London).

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Abstract

The telomere bouquet is a highly conserved structure specific to meiotic prophase in which the telomeres are gathered to a limited region of the nuclear periphery. In a number of organisms including fission yeast, the bouquet is tethered to the spindle pole body (SPB) or centrosome. The meiosis-specific factors Bqt1/Bqt2 function as a bridge to connect the telomere proteins Taz1/Rap1 to the SPB. Deletion of any of these elements disrupts the bouquet, leading to defective spindle formation and aberrant meiosis (Tomita and Cooper, 2007). The aim of this thesis was to determine the molecular basis for control of the meiotic spindle by the telomere bouquet. We asked the question: how does the meiotic SPB differ in the presence and absence of bouquet function? Using methods to quantify SPB component levels via fluorescence microscopy in live cells, we found that bouquet-defective strains show a slight elevation of the level of Pcp1, an SPB component, but such elevation is not enough to confer bouquet-mutant phenotypes in bouquet-proficient backgrounds. Indeed, our data suggest that in the absence of the bouquet, SPB duplication occurs properly and with normal timing. However, we observed that the separation of the duplicated SPBs is markedly abnormal, as the duplicated SPBs fail to remain apart and at least one of them often becomes dislodged from the nucleus. Moreover, the γ-tubulin complex fails to localise to both spindle poles. Hence, the duplicated SPBs fail to properly recruit the γ-tubulin complex. We thus investigated the molecular mechanism underlying control of γ-tubulin complex recruitment by the bouquet. Our findings allow us to propose a model that explains the different types of spindle defects seen in the absence of the bouquet.

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