Biomedical subjects

J P Aumais

Publications and source records attributed to J P Aumais.

4 recordsLinked to original sources

PubMed2001

NudC associates with Lis1 and the dynein motor at the leading pole of neurons.

NUDC is a highly conserved protein important for nuclear migration and viability in Aspergillus nidulans. Mammalian NudC interacts with Lis1, a neuronal migration protein important during neocorticogenesis, suggesting a conserved mechanism of nuclear movement in A. nidulans and neuronal migration in the developing mammalian brain (S. M. Morris et al., 1998). To further investigate this possibility, we show for the first time that NudC, Lis1, and cytoplasmic dynein intermediate chain (CDIC) colocalize at the microtubule organizing center (MTOC) around the nucleus in a polarized manner facing the leading pole of cerebellar granule cells with a migratory morphology. In neurons with stationary morphology, NudC is distributed throughout the soma and colocalizes with CDIC and tubulin in neurites as well as at the MTOC. At the subcellular level, NudC, CDIC, and p150 dynactin colocalize to the interphase microtubule array and the MTOC in fibroblasts. The observed colocalization is confirmed biochemically by coimmunoprecipitation of NudC with CDIC and cytoplasmic dynein heavy chain (CDHC) from mouse brain extracts. Consistent with its expression in individual neurons, a high level of NudC is detected in regions of the embryonic neocortex undergoing extensive neurogenesis as well as neuronal migration. These data suggest a biochemical and functional interaction of NudC with Lis1 and the dynein motor complex during neuronal migration in vivo.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2001

NUDC expression during amphibian development.

To identify gene products important for gastrulation in the amphibian Pleurodeles waltl, a screen for regional differences in new protein expression at the early gastrula stage was performed. A 45 kDa protein whose synthesis was specific for progenitor endodermal cells was identified. Microsequencing and cDNA cloning showed that P45 is highly homologous to rat NUDC, a protein suggested to play a role in nuclear migration. Although PNUDC can be detected in all regions of the embryo, its de novo synthesis is tightly regulated spatially and temporally throughout oogenesis and embryonic development. New PNUDC synthesis in the progenitor endodermal cells depends on induction by the mesodermal cells in the gastrula. During development, PNUDC is localized in the egg cortical cytoplasm, at the cleavage furrow during the first embryonic division, around the nuclei and cortical regions of bottle cells in the gastrula, and at the basal region of polarized tissues in the developing embryo. These results show for the first time the expression and compartmentalization of PNUDC at distinct stages during amphibian development.

Amino Acid Sequence↗

PubMed1997

Selective interaction of hsp90 with an estrogen receptor ligand-binding domain containing a point mutation.

The 90-kDa heat shock protein (hsp90) has been implicated in modulating steroid receptor function in vitro and in vivo. Previous studies have suggested that hsp90 interacts with large portions of the estrogen receptor (ER) ligand-binding domain and sequences of the receptor required for stable DNA binding. To characterize the interaction of the ER ligand-binding domain with hsp90, we have compared the properties of chimeras created by coupling the ligand-binding domain to the constitutive transactivator VP16-GAL. Two types of chimeras were created: VP16-GAL-ERG, containing the wild-type ligand-binding domain derived from the cDNA HEG0, and VP16-GAL-ERV, containing the substitution G400V derived from the ligand-binding domain of the original ER cDNA isolate, HE0. The G400V mutation alters the physical properties of VP16-GAL-ERV by rendering it hormone-dependent for DNA binding and more strongly dependent on estradiol for transactivation compared with VP16-GAL-ERG. Glycerol gradient analyses and chemical cross-linking/coimmunoprecipitation showed that, unlike VP16-GAL-ERG, VP16-GAL-ERV formed stable complexes with hsp90 in vitro. These data show that hsp90 selectively recognizes the altered ER ligand-binding domain containing the G400V substitution and indicate that the wild-type ER ligand-binding domain of VP16-GAL-ERG does not interact with hsp90 in vitro. Hormone binding studies showed that the ligand-binding domain of VP16-GAL-ERV was destabilized by incubation in the presence of high concentrations of salt or in the absence of sodium molybdate, conditions that disrupt its interaction with hsp90. The ligand-binding domain of the Val-400 ER thus behaves similarly to that of the wild-type glucocorticoid receptor, which has previously been shown to interact with hsp90 in vitro. These results provide evidence for the action of hsp90 as a molecular chaperone by selectively recognizing destabilized proteins.

Animals↗

PubMed1996

Function of directly repeated half-sites as response elements for steroid hormone receptors.

The mouse mammary tumor virus promoter has been shown to be inducible by glucocorticoids and progesterone. Although steroid hormone receptors bind with high affinity to palindromic response elements, the hormone-responsive region of the mouse mammary tumor virus promoter contains a pair of directly repeated half-sites that are important for hormone inducibility. Recent experiments have also indicated that direct repeats can function as estrogen response elements. Here, we have investigated DNA binding by steroid receptors to direct repeats and provide evidence using gel retardation assays, methylation interference, and gene transfer experiments that direct repeats of TGTTCT or RGGTCA motifs function as response elements for glucocorticoid (GR) or estrogen receptors (ER), respectively, by binding receptor homodimers. Specific GR- or ER-DNA complexes were observed on direct repeats with different spacings between half-sites, indicating that binding of steroid receptors to direct repeats is more flexible than binding to palindromic elements. This flexibility was further emphasized by the observation that the GR could also bind to everted repeats of TGTTCT motifs separated by 9 base pairs. The isolated DNA binding domains of the GR and ER bound cooperatively to palindromes, but no evidence was observed for cooperative binding to direct repeats. Under similar conditions the DNA binding domains of retinoid receptors retinoid X receptor and retinoic acid receptor bound to direct repeats cooperatively as heterodimers. Similarly, ER derivative HE15, which lacks a functional ligand binding domain, bound palindromic response elements but failed to bind direct repeats. These results indicate that the dimerization domain in the ligand binding domain is essential for binding of steroid receptors to direct repeats and that the dimerization domain in the D-box of the DNA binding is not functional under these conditions. Moreover, the results suggest that steroid receptor DNA binding domains may lack dimerization domains outside the D-box, which would function in binding to direct repeats, in contrast to receptors for retinoids and thyroid hormone. A comparison of the mechanisms of binding of steroid receptors and retinoid and thyroid hormone receptors to direct repeats is presented.

Animals↗