7,368 research outputs found
Different domains cooperate to target the human ribosomal L7a protein to the nucleus and to the nucleoli.
The human ribosomal protein L7a is a component of the major ribosomal subunit. We transiently expressed in HeLa cells L7a-β-galactosidase fusion proteins and studied their subcellular localization by indirect immunofluorescence staining with anti-β-galactosidase antibodies. We have identified three distinct domains responsible for the nuclear targeting of the protein: domain I, amino acids 23-51; domain II, amino acids 52-100; domain III, amino acids 101-220, each of which contains at least one nuclear localization signal (NLS). Through subcellular localization analysis of deletion mutants of L7a-β-galactosidase chimeras, we demonstrate that domain II plays a special role because it is necessary, although not sufficient, to target the chimeric β-galactosidase to the nucleoli. In fact, we demonstrate that the nucleolar targeting process requires the presence of domain II plus an additional basic domain that can be represented by an NLS or a basic stretch of amino acids without NLS activity. Thus, when multiple NLS are present, each NLS exerts distinct functions. Domain II drives nucleolar accumulation of a reporter protein with the cooperative action of a short basic amino acid sequence, suggesting a mechanism requiring protein-protein or protein-nucleic acid interactions
The electronic structure of liquid water within density functional theory
In the last decade, computational studies of liquid water have mostly
concentrated on ground state properties. However recent spectroscopic
measurements have been used to infer the structure of water, and the
interpretation of optical and x-ray spectra requires accurate theoretical
models of excited electronic states, not only of the ground state. To this end,
we investigate the electronic properties of water at ambient conditions using
ab initio density functional theory within the generalized gradient
approximation (DFT/GGA), focussing on the unoccupied subspace of Kohn-Sham
eigenstates. We generate long (250 ps) classical trajectories for large
supercells, up to 256 molecules, from which uncorrelated configurations of
water molecules are extracted for use in DFT/GGA calculations of the electronic
structure. We find that the density of occupied states of this molecular liquid
is well described with 32 molecule supercells using a single k-point (k = 0) to
approximate integration over the first Brillouin zone. However, the description
of the density of unoccupied states (u-EDOS) is sensitive to finite size
effects. Small, 32 molecule supercell calculations, using Gamma-the point
approximation, yield a spuriously isolated state above the Fermi level.
Nevertheless, the more accurate u-EDOS of large, 256 molecule supercells may be
reproduced using smaller supercells and increased k-point sampling. This
indicates that the electronic structure of molecular liquids like water is
relatively insensitive to the long-range disorder in the molecular structure.
These results have important implications for efficiently increasing the
accuracy of spectral calculations for water and other molecular liquids.Comment: 12 pages, 11 figures (low quality) Submitted to JChemPhy
The laminA/NF-Y protein complex reveals an unknown transcriptional mechanism on cell proliferation
Lamin A is a component of the nuclear matrix that also controls proliferation by
largely unknown mechanisms. NF-Y is a ubiquitous protein involved in cell proliferation
composed of three subunits (-YA -YB -YC) all required for the DNA binding and
transactivation activity. To get clues on new NF-Y partner(s) we performed a mass
spectrometry screening of proteins that co-precipitate with the regulatory subunit
of the complex, NF-YA. By this screening we identified lamin A as a novel putative
NF-Y interactor. Co-immunoprecipitation experiments and confocal analysis confirmed
the interaction between the two endogenous proteins. Interestingly, this association
occurs on euchromatin regions, too. ChIP experiments demonstrate lamin A
enrichment in several promoter regions of cell cycle related genes in a NF-Y dependent
manner. Gain and loss of function experiments reveal that lamin A counteracts NF-Y
transcriptional activity. Taking advantage of a recently generated transgenic reporter
mouse, called MITO-Luc, in which an NF-Y–dependent promoter controls luciferase
expression, we demonstrate that lamin A counteracts NF-Y transcriptional activity
not only in culture cells but also in living animals. Altogether, our data demonstrate
the occurrence of lamin A/NF-Y interaction and suggest a possible role of this protein
complex in regulation of NF-Y function in cell proliferatio
How Do Maternal Subclinical Symptoms Influence Infant Motor Development during the First Year of Life?
An unavoidable reciprocal influence characterizes the mother-child dyad. Within this relationship, the presence of depression, somatization, hostility, paranoid ideation, and interpersonal sensitivity symptoms at a subclinical level and their possible input on infant motor competences has not been yet considered. Bearing in mind that motor abilities represent not only an indicator of the infant\u2019s health-status, but also the principal field to infer his/her needs, feelings and intentions, in this study the quality of infants\u2019 movements were assessed and analyzed in relationship with the maternal attitudes. The aim of this research was to investigate if/how maternal symptomatology may pilot infant\u2019s motor development during his/her first year of life by observing the characteristics of motor development in infants aged 0\u201311 months. Participants included 123 mothers and their infants (0\u201311 months-old). Mothers\u2019 symptomatology was screened with the Symptom Checklist-90-Revised (SCL-90-R), while infants were tested with the Peabody Developmental Motor Scale-Second Edition. All dyads belonged to a non-clinical population, however, on the basis of SCL-90-R scores, the mothers\u2019 sample was divided into two groups: normative and subclinical. Descriptive, t-test, correlational analysis between PDMS-2 scores and SCL-90-R results are reported, as well as regression models results. Both positive and negative correlations were found between maternal perceived symptomatology, Somatization (SOM), Interpersonal Sensitivity (IS), Depression (DEP), Hostility (HOS), and Paranoid Ideation (PAR) and infants\u2019 motor abilities. These results were further verified by applying regression models to predict the infant\u2019s motor outcomes on the basis of babies\u2019 age and maternal status. The presence of positive symptoms in the SCL-90-R questionnaire (subclinical group) predicted good visual-motor integration and stationary competences in the babies. In particular, depressive and hostility feelings in mothers seemed to induce an infant motor behavior characterized by a major control of the environmental space. When mothers perceived a higher level of hostility and somatization, their babies showed difficulties in sharing action space, such as required in the development of stationary positions and grasping abilities. In a completely different way, when infants can rely on a mother with low-perceived symptoms (normative group) his/her motor performances develop with a higher degree of freedom/independence. These findings suggest, for the first time, that even in a non- clinical sample, mother\u2019s perceived-symptoms can produce important consequences not in infant motor development as a whole, but in some specific areas, contributing to shape the infant\u2019s motor ability and his/her capability to act in the world
cis-acting sequences and trans-acting factors in the localization of mRNA for mitochondrial ribosomal proteins
mRNA localization is a conserved post-transcriptional process crucial for a variety of systems. Although several mechanisms have been identified, emerging evidence suggests that most transcripts reach the protein functional site by moving along cytoskeleton elements. We demonstrated previously that mRNA for mitochondrial ribosomal proteins are asymmetrically distributed in the cytoplasm, and that localization in the proximity of mitochondria is mediated by the 3′-UTR. Here we show by biochemical analysis that these mRNA transcripts are associated with the cytoskeleton through the microtubule network. Cytoskeleton association is functional for their intracellular localization near the mitochondrion, and the 3′-UTR is involved in this cytoskeleton-dependent localization. To identify the minimal elements required for localization, we generated DNA constructs containing, downstream from the GFP gene, deletion mutants of mitochondrial ribosomal protein S12 3′-UTR, and expressed them in HeLa cells. RT-PCR analysis showed that the localization signals responsible for mRNA localization are located in the first 154 nucleotides. RNA pulldown assays, mass spectrometry, and RNP immunoprecipitation assay experiments, demonstrated that mitochondrial ribosomal protein S12 3′-UTR interacts specifically with TRAP1 (tumor necrosis factor receptor-associated protein1), hnRNPM4 (heterogeneous nuclear ribonucleoprotein M4), Hsp70 and Hsp60 (heat shock proteins 70 and 60), and α-tubulin in vitro and in vivo
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