Dynamic relocalization of yeast cell cycle regulator, Hsl7

Hsl7 protein, fused to the Green Fluorescent Protein (GFP), is visualized by fluorescence microscopy (upper panels). GFP-Hsl7 appears as a "dot" in cells immediately after completion of cell division because it associates with the spindle pole body (the major microtubule-organizing center in yeast cells), situated on the nuclear envelope. Later in the cell cycle, however, Hsl7 is released from the spindle pole body and associates with the collar of septin filaments on the daughter side of the bud neck (upper right panel). The filaments composed of septin proteins demarcate the site where cell division will eventually occur. Nuclei (large bluish-white ball) in the same cells (lower panels) were visualized by staining with a DNA-specific fluorescent dye (DAPI); the small dots represent mitochondrial DNA. This is part of the research in the laboratory of Jeremy Thorner in the Department of Molecular and Cell Biology.