18,539 research outputs found
Recommended from our members
Identification of an interchromosomal compartment by polymerization of nuclear-targeted vimentin
A number of structural and functional subnuclear compartments have been described, including regions
exclusive of chromosomes previously hypothesized to form
a reactive nuclear space. We have now explored this
accessible nuclear space and interchromosomal
nucleoplasmic domains experimentally using Xenopus
vimentin engineered to contain a nuclear localization signal
(NLS-vimentin). In stably transfected human cells
incubated at 37°C, the NLS-vimentin formed a restricted
number of intranuclear speckles. At 28°C, the optimal
temperature for assembly of the amphibian protein, NLSvimentin
progressively extended with time out from the
speckles into strictly orientated intranuclear filamentous
arrays. This enabled us to observe the development of a
system of interconnecting channel-like areas. Quantitative
analysis based on 3-D imaging microscopy revealed that
these arrays were localized almost exclusively outside of
chromosome territories. During mitosis the filaments
disassembled and dispersed throughout the cytoplasm,
while in anaphase-telophase the vimentin was recruited
back into the nucleus and reassembled into filaments at the
chromosome surfaces, in distributions virtually identical to
those observed in the previous interphase. The filaments
also colocalized with specific nuclear RNAs, coiled bodies
and PML bodies, all situated outside of chromosome
territories, thereby interlinking these structures. This
strongly implies that these nuclear entities coexist in the
same interconnected nuclear compartment. The
assembling NLS-vimentin is restricted to and can be used
to delineate, at least in part, the formerly proposed
reticular interchromosomal domain compartment (ICD).
The properties of NLS-vimentin make it an excellent tool
for performing structural and functional studies on this
compartment
Cmr1/WDR76 defines a nuclear genotoxic stress body linking genome integrity and protein quality control
DNA replication stress is a source of genomic instability. Here we identify changed mutation rate 1 (Cmr1) as a factor involved in the response to DNA replication stress in Saccharomyces cerevisiae and show that Cmr1—together with Mrc1/Claspin, Pph3, the chaperonin containing TCP1 (CCT) and 25 other proteins—define a novel intranuclear quality control compartment (INQ) that sequesters misfolded, ubiquitylated and sumoylated proteins in response to genotoxic stress. The diversity of proteins that localize to INQ indicates that other biological processes such as cell cycle progression, chromatin and mitotic spindle organization may also be regulated through INQ. Similar to Cmr1, its human orthologue WDR76 responds to proteasome inhibition and DNA damage by relocalizing to nuclear foci and physically associating with CCT, suggesting an evolutionarily conserved biological function. We propose that Cmr1/WDR76 plays a role in the recovery from genotoxic stress through regulation of the turnover of sumoylated and phosphorylated proteins
Nuclear astrophysics studies with ultra-peripheral heavy-ion collisions
I describe in very simple terms the theoretical tools needed to investigate
ultra-peripheral nuclear reactions for nuclear astrophysics purposes. For a
more detailed account, see arXiv:0908.4307.Comment: 12 pages, 8 figures, Lecture notes presented at the 5th European
Summer School on Experimental Nuclear Astrophysics, Sep. 20- 27, 2009, Santa
Tecla, Sicily, Italy. AIP proceedings, to be publishe
Manifestation of finite temperature size effects in nanogranular magnetic graphite
In addition to the double phase transition (with the Curie temperatures
T_C=300K and T_{Ct}=144K), a low-temperature anomaly in the dependence of the
magnetization is observed in the bulk magnetic graphite (with an average
granular size of L=10nm), which is attributed to manifestation of the size
effects below the quantum temperature. The best fits of the high-temperature
data (using the mean-field Curie-Weiss and Bloch expressions) produced
reasonable estimates for the model parameters, such as defects mediated
effective spin exchange energy J=12meV (which defines the intragranular Curie
temperature T_C) and proximity mediated interactions between neighboring grains
(through potential barriers created by thin layers of non-magnetic graphite)
with energy J_t=exp(-d/s)J=5.8meV (which defines the intergranular Curie
temperature T_{Ct}) with d=1.5nm and s=2nm being the intergranular distance and
characteristic length, respectively
Bicarbonate-responsive “soluble” adenylyl cyclase defines a nuclear cAMP microdomain
Bicarbonate-responsive “soluble” adenylyl cyclase resides, in part, inside the mammalian cell nucleus where it stimulates the activity of nuclear protein kinase A to phosphorylate the cAMP response element binding protein (CREB). The existence of this complete and functional, nuclear-localized cAMP pathway establishes that cAMP signals in intracellular microdomains and identifies an alternate pathway leading to CREB activation
- …