Structures and oxide mobility in Bi-Ln-O materials: heritage of Bi2O3.
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Journal Article↗
Biomedical subjects
Pascal Roussel
Publications and source records attributed to Pascal Roussel.
A B23-interacting sequence as a tool to visualize protein interactions in a cellular context.
We report the characterization of a nucleolar localization sequence (NoLS) that targets the green fluorescent protein (GFP) into the granular component (GC) of nucleoli. This NoLS interacts in vitro specifically and directly with the major nucleolar protein B23 and more precisely with the region of B23 including the two acidic stretches. The affinity of NoLS for B23 is stronger than that of the HIV-1 Rev protein in vitro. Moreover, B23-NoLS interaction also occurs in vivo. Indeed, (1) NoLS confers on the GFP the behavior of B23 throughout the cell cycle, (2) the GFP-NoLS fusion and B23 remain colocalized after drug treatments, (3) a selective delocalization of B23 from nucleoli to nucleoplasm induces a concomitent delocalization of the GFP-NoLS fusion, and (4) the fusion of NoLS to fibrillarin makes it possible to colocalize fibrillarin and B23. Interestingly, by fusing NoLS to fibrillarin, both fibrillarin and the fibrillarin partner Nop56 are mislocalized in the GC of nucleoli. Similarly, by fusing the NoLS to MafG, part of the nuclear transcription factor NF-E2 composed of both MafG and p45 NF-E2, NF-E2 is redirected from the nucleoplasm to the nucleoli. Thus, we propose that the NoLS may be used as a tool to visualize and prove protein interactions in a cellular context.
Animals↗
Host-guest interaction in a thiourea-dimethyl oxalate (2/1) complex at 300 and 100 K.
The title complex, 2CH4N2S.C4H6O4, is a host-guest system. The asymmetric unit consists of one complete thiourea molecule and one-half of a dimethyl oxalate molecule lying on an inversion centre. The host thiourea molecules are connected to form zigzag chains by N-H...S hydrogen bonds. The guest dimethyl oxalate molecules provide O-atom acceptors for N-H...O hydrogen bonds, thus interconnecting the chains of thiourea molecules to form completely connected sheets. The reduction in temperature from 300 to 100 K leaves the structure unchanged and still isostructural with that previously determined for the analogous thiourea-diethyl oxalate (2/1) complex. It does, however, induce closer packing of the molecules, general shrinkage of the unit cell and shortening of the hydrogen bonds, these last two to the extent of 1-2%.
Journal Article↗
Regulators of nucleolar functions.
The nucleolus is the ribosome factory and also a multifunctional domain that plays an important role in nuclear organization and function. Interestingly, ribosome biogenesis appears directly related to cell growth and proliferation. The nucleolus corresponds to a very dynamic nuclear domain resulting from an equilibrium between the level of ribosomal RNA synthesis and the efficiency of ribosomal RNA processing. Ribosome biogenesis is regulated throughout interphase and stops during mitosis. The mitotic silencing of transcription, the distribution of the processing machinery, as well as the link between transcription and processing were found to be dependent on cyclin-dependent kinase(s).
Animals↗
Emerging concepts of nucleolar assembly.
The nucleolus is a large nuclear domain and the site of ribosome biogenesis. It is also at the parting of the ways of several cellular processes, including cell cycle progression, gene silencing, and ribonucleoprotein complex formation. Consequently, a functional nucleolus is crucial for cell survival. Recent investigations of nucleolar assembly during the cell cycle and during embryogenesis have provided an integrated view of the dynamics of this process. Moreover, they have generated new ideas about cell cycle control of nucleolar assembly, the dynamics of the delivery of the RNA processing machinery, the formation of prenucleolar bodies, the role of precursor ribosomal RNAs in stabilizing the nucleolar machinery and the fact that nucleolar assembly is completed by cooperative interactions between chromosome territories. This has opened a new area of research into the dynamics of nuclear organization and the integration of nuclear functions.
Animals↗
Cyclin-dependent kinases govern formation and maintenance of the nucleolus.
In higher eukaryotic cells, the nucleolus is a nuclear compartment assembled at the beginning of interphase, maintained during interphase, and disorganized during mitosis. Even if its structural organization appears to be undissociable from its function in ribosome biogenesis, the mechanisms that govern the formation and maintenance of the nucleolus are not elucidated. To determine if cell cycle regulators are implicated, we investigated the putative role of the cyclin-dependent kinases (CDKs) on ribosome biogenesis and nucleolar organization. Inhibition of CDK1-cyclin B during mitosis leads to resumption of rDNA transcription, but is not sufficient to induce proper processing of the pre-rRNA and total relocalization of the processing machinery into rDNA transcription sites. Similarly, at the exit from mitosis, both translocation of the late processing machinery and pre-rRNA processing are impaired in a reversible manner by CDK inhibitors. Therefore, CDK activity seems indispensable for the building of functional nucleoli. Furthermore, inhibition of CDKs in interphasic cells also hampered proper pre-rRNA processing and induced a dramatic disorganization of the nucleolus. Thus, we propose that the mechanisms governing both formation and maintenance of functional nucleoli involve CDK activities and couple the cell cycle to ribosome biogenesis.
CDC2 Protein Kinase↗