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The Neurospora crassa Asm-1 + (ascospore maturation 1) gene encodes an abundant nucleus-localized protein required for formation of female structures and for ascospore maturation. Deletion mutants of Asm-1 + are ''ascus-dominant,'' i.e., when crossed to wild-type, neither Asm-1 + nor Asm-1 Δ spores mature. To explain this behavior, we considered three models: an effect...
A murine model of ataxia telangiectasia was created by disrupting the Atm locus via gene targeting. Mice homozygous for the disrupted Atm allele displayed growth retardation, neurologic dysfunction, male and female infertility secondary to the absence of mature gametes, defects in T lymphocyte maturation, and extreme sensitivity to γ-irradiation. The majority of animals developed malignant thymic...
Inheritance of the active and inactive states of gene expression by individual cells is crucial for development. In fission yeast, mating-type region consists of three loci called mat1, mat2, and mat3. Transcriptionally silent mat2 and mat3 loci are separated by a 15 kb interval, designated the K-region, and serve as donors of information for transcriptionally active mat1 interconversion. In a strain...
Aniridia in man and Small eye in mice are semidominant developmental disorders caused by mutations within the paired box gene PAX6. Whereas heterozygotes suffer from iris hypoplasia, homozygous mice lack eyes and nasal cavities and exhibit brain abnormalities. To investigate the role of gene dosage in more detail, we have generated yeast artificial chromosome transgenic mice carrying the human PAX6...
X inactivation results in inactivation of one X chromosome to compensate for gene dosage differences between mammalian females and males. It requires the X-inactivation center (Xic) and Xist in cis. We report that introducing 450 kb of murine Xic/Xist sequences onto autosomes activates female dosage compensation in male ES cells. Xist is induced upon differentiation and can be expressed from both...
Autocatalytic processing mediated by the carboxy-terminal domain of the hedgehog (hh) protein precursor (Hh) generates an amino-terminal product that accounts for all known signaling activity. The role of autoprocessing in biogenesis of the hh signal has been unclear, since a truncated unprocessed protein lacking all carboxy-terminal domain sequences retains signaling activity. Here, we present evidence...
A cell-free system based on cytosols of normally growing cells is established that reproduces aspects of the apoptotic program in vitro. The apoptotic program is initiated by addition of dATP. Fractionation of cytosol yielded a 15 kDa protein that is required for in vitro apoptosis. The absorption spectrum and protein sequence revealed that this protein is cytochrome c. Elimination of cytochrome c...
Eph family receptor tyrosine kinases have been proposed to control axon guidance and fasciculation. To address the biological functions of the Eph family member Nuk, two mutations in the mouse germline have been generated: a protein null allele (Nuk 1 ) and an allele that encodes a Nuk-βgal fusion receptor lacking the tyrosine kinase and C-terminal domains (Nuk lacZ ...
We have investigated the mechanism that enables achiasmate chromosomes to segregate from each other at meiosis I in D. melanogaster oocytes. Using novel cytological methods, we asked whether nonexchange chromosomes are paired prior to disjunction. Our results show that the heterochromatin of homologous chromosomes remains associated throughout prophase until metaphase I regardless of whether they...
In tomato, resistance to Pseudomonas syringae pv. tomato (Pst) strains expressing the avirulence gene avrPto requires the presence of at least two host genes, designated Pto and Prf. Here we report that Prf encodes a protein with leucine-zipper, nucleotide binding, and leucine-rich repeat motifs, as are found in a number of resistance gene products from other plants. prf mutant alleles (4) were found...
Arabidopsis COP9 is a component of a large protein complex that is essential for the light control of a developmental switch and whose conformation or size is modulated by light. The complex is acidic, binds heparin, and is localized within the nucleus. Biochemical purification of the complex to near homogeneity revealed that it contains 12 distinct subunits. One of the other subunits is COP11, mutations...
The T cell leukemia oncoprotein SCL/tal-1, a basic-helix-loop-helix transcription factor, is required for production of embryonic red blood cells in the mouse yolk sac. To define roles in other lineages, we studied the hematopoietic potential of homozygous mutant SCL/tal-1 -/- embryonic stem cells upon in vitro differentiation and in vivo in chimeric mice. Here we show that in the absence of SCL/tal-1,...
To identify genes important for human cognitive development, we studied Williams syndrome (WS), a developmental disorder that includes poor visuospatial constructive cognition. Here we describe two families with a partial WS phenotype; affected members have the specific WS cognitive profile and vascular disease, but lack other WS features. Submicroscopic chromosome 7q11.23 deletions cosegregate with...
T cell development is regulated at two major control points where maturation, proliferation, and antigen receptor gene rearrangement are coordinated. Progression through these developmental control points is dependent upon the expression of different forms of the T cell receptor. Here we show that the MAP kinase cascade is a regulator of the differentiation of immature thymocytes from double-negative...
The three-dimensional structure of Escherichia coli 3-methyladenine DNA glycosylase II, which removes numerous alkylated bases from DNA, was solved at 2.3 Å resolution. The enzyme consists of three domains: one α + β fold domain with a similarity to one-half of the eukaryotic TATA box-binding protein, and two all α-helical domains similar to those of Escherichia coli endonuclease III with combined...
We describe the complete β-tubulin folding pathway. Folding intermediates produced via ATP-dependent interaction with cytosolic chaperonin undergo a sequence of interactions with four proteins (cofactors A,D, E, and C). The postchaperonin steps in the reaction cascade do not depend on ATP or GTP hydrolysis, although GTP plays a structural role in tubulin folding. Cofactors A and D function by capturing...
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