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A M Billi

Publications and source records attributed to A M Billi.

41 records · Page 3Linked to original sources
PubMed1986

Changes in nucleosome structure and histone H3 accessibility. Iodoacetamidofluorescein labelling after treatment with phosphatidylserine vesicles.

The accessibility of the sulfhydryl-specific dye 6-iodoacetamidofluorescein (IAF) to H3 histone has been studied in isolated rat liver nuclei and mononucleosomal core particles after treatment with phosphatidylserine (PS) multilamellar vesicles (MLV). In isolated nuclei, despite the enhancement of total RNA synthesis and the massive chromatin decondensation produced by liposomes, the amount of histone H3 which can be labelled with the dye remains essentially the same in PS-treated as in control nuclei. However, when mononucleosomal core particles, treated with PS vesicles, are reacted with IAF, H3 becomes derivatized by the dye, while controls do not. These data provide additional evidence that the metabolic and structural changes observed in isolated nuclei treated with PS MLV, are due mainly to the reported removal of histone H1. Moreover, the experiments reported confirm the usefulness of IAF in studying the changes of nucleosome organization, since PS is able to affect the nucleosomal core configuration in isolated nucleosome particles, derivatizing the buried cysteine groups of H3 histone.

Animals↗
PubMedDate not supplied

Nuclear phospholipase C: a novel aspect of phosphoinositide signalling.

The role of polyphosphoinositides in cellular signalling is well known and recently it has also been shown that the nucleus is a site for both synthesis and hydrolysis of the phosphorylated forms of phosphatidylinositol. It has been demonstrated that phospholipase C specific for inositol lipids (PLC) is one of the main steps of the inositol lipid cycle. The PLC beta family, and especially type beta 1, has given rise to considerable interest since, due to their common COOH-terminus they show nuclear localisation in addition to that at the plasma membrane. It is well established that an autonomous intranuclear inositide cycle exists, and that this cycle is endowed with conventional lipid kinases, phosphatases and PLCs. Among this latter the beta 1 type undergoes stimulation or inhibition under different stimuli and this implicates the beta 1 isoform as a key enzyme for mitogen-activated cell growth as well as for differentiation. Indeed, both the overexpression and the down-regulation of PLC beta 1, by means of antisense mRNA, have demonstrated that PLC plays a role in the nuclear compartment.

Animals↗
PubMedDate not supplied

Further considerations on the intranuclear distribution of HMGI/Y proteins.

We have investigated the intranuclear distribution of High-mobility group proteins I/Y by means of immunofluorescent staining employing a variety of cell lines. Confocal scanning laser microscopy analysis revealed that High-mobility group proteins I/Y are present in an intranuclear fibrogranular network and mitotic chromosomes. In Caski, C4I, Flow 2002, and K562 cell lines, High-mobility group proteins I/Y were absent from nucleoli, whereas in HeLa cells they were present in this nuclear domain. Double immunolabeling studies showed that High-mobility group proteins I/Y co-localize with other key nuclear components such as NuMA, SC-35, and TAF(II)70. Nuclear reactivity for High-mobility group proteins I/Y dramatically decreased in apoptotic nuclei of HL-60 human leukemia cells. Our morphological data correlate well with previous biochemical and functional findings obtained by other investigators, who have demonstrated multiple roles for this class of polypeptides. However, they point to the likelihood that High-mobility group proteins I/Y are involved in as yet unidentified functions, most likely in the speckle domains of the nucleus. They also show that conceivably these proteins are also involved in apoptosis.

Antigens, Nuclear↗
PubMedDate not supplied

Nuclear inositol lipid cycle: a new central intermediary in signal transduction.

The involvement of phospholipids and especially polyphosphoinositides in cellular signalling has been documented in detail over the last 20 years. Besides the membrane localisation the nucleus also has been show to be a site for both the synthesis and hydrolysis of the phosphorylated forms of phosphatidylinositol. Previous observations dealing with signal transduction have established phospholipase C, specific for inositol lipids (PLC), an important step in the inositol lipid cycle. Of the several known PLC isoforms the type beta 1 is of particular interest because of its reported nuclear localisation, in addition to its presence at the plasma membrane. Indeed, investigations from our laboratory and others have shown the existence in several cell types of an autonomous intranuclear inositide cycle endowed with both conventional lipid kinases and PLC. Moreover, both the stimulation and the inhibition of the nuclear PLC beta 1 under different stimuli implicate this PLC isoform as a key enzyme for mitogen-activated cell growth as well as for differentiation. These findings have prompted us to better characterise the nuclear PLC beta 1. The isoform beta 1 has been studied as a possible target for anti-cancer drugs and as an inducer, via diacylglycerol generation, of the translocation of specific protein kinase C (PKC) isozyme to the nucleus. The chromosome mapping of PLC beta 1 gene has been carried out and the effect of its knock-out by means of antisense cDNA has been determined.

3T3 Cells↗