Introduction Phosphoinositides (PIPns) are negatively charged phospholipids mainly found at the cytosolic surface of membranes. They are considered as minor components of cell membranes because they represent less than a 15 % of the total phospholipids found in eukaryotic cells. However, phosphoinositides are recognised as direct signalling molecules, which can act as second messengers by interacting with effector proteins either electrostatically or via specific phosphoinositides binding

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... s. This family of lipids is formed from seven members, phosphorylated in different positions, which are constantly being turned over by an array of kinases and phosphatases. Each of them has a unique subcellular distribution (1). Moreover, the existence of a nuclear pool of phosphoinositides (2) has been described, whose physical state and location has been a matter of controversy, but they are part of the nucleoplasm and perhaps located on invaginations of the nuclear envelope (NE) that penetrate the nucleus. These invaginations are known as the nucleoplasmic reticula. The roles of phosphoinositides inside the nucleus are unclear but in DNA and RNA polymerase activity upon the addition of phospholipids changes have been observed (3). Lately, it has also been demonstrated that they play important roles in membrane dynamics (4). Recent studies have shown that the NE formation is also dependent on these phospholipids (5). In order to investigate the detailed mechanism of the NE assembly, cell-free systems, which mimic the steps of the NE assembly have been used. These systems have shown that there is a NE precursor membrane vesicle population (MV1), that does not derive from the endoplasmic reticulum (ER), but is essential to the NE assembly and is highly enriched in PIPns (up to a 60 mol %) (5). The NE formation is a vital process that occurs in every mitotic cycle and during fertilisation, and defects induce diseases, such as specific cancers or premature aging diseases (6).