Life cycles of yeast spindle pole bodies: Getting microtubules into a closed nucleus

The spindle pole body (SPB) is the principal microtubule organizing center of budding and fission yeast. We have examined SPBs and their associated mi crotubules from both organisms, using electron microscopy and three-dimensi onal reconstruction techniques, to identify the structural changes that acc ompany progression through the cell cycle. In this report, we compare these changes in the two kinds of yeasts and present a model for how microtubule s get into a closed nucleus. (C) 1999 Editions scientifiques et medicales E lsevier SAS.