Non-membranous granular organelle consisting of PCM-1: subcellular distribution and cell-cycledependent assembly/disassembly

Centriolar satellites were initially identified as electrondense spherical granules, similar to70-100 nm diameter, localized around the centrosomes. We have previously identified pericentriolar material 1 (PCM-1), with a molecular mass of similar to230 kDa, as a component of centriolar satellites. We now show by immunofluorescence microscopy that these granules are not only concentrated around centrioles but also scattered throughout the cytoplasm in various types of mouse cells, leading us tentatively to call them `PCM-1 granules'. We then found that, when overexpressed, PCM-1 molecules lacking their C-terminal region bound directly with each other through two distinct regions to form large aggregates, which then recruited endogenous PCM-1. These large aggregates as well as endogenous PCM-1.