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The hematopoietic transcription factor GATA-1 is essential for development of the erythroid and megakaryocytic lineages. Using the conserved zinc finger DNA-binding domain of GATA-1 in the yeast two- hybrid system, we have identified a novel, multitype zinc finger protein, Friend of GATA-1 (FOG), which binds GATA-1 but not a functionally inactive mutant lacking the amino (N) finger. FOG is coexpressed...
We describe the purification and characterization of ACF, an ATP-utilizing chromatin assembly and remodeling factor.ACF is a multisubunit factor that contains ISWI protein and is distinct from NURF, another ISWI- containing factor. In chromatin assembly, purified ACF and a core histone chaperone (such as NAP-1 or CAF-1) are sufficient for the ATP-dependent formation of periodic nucleosome arrays....
Novel utilization of the coiled-coil motif is presented that enables TlpA, an autoregulatory repressor protein in Salmonella, to sense temperature shifts directly and therebyto modulate the extent of transcription repression. Salmonella cells shifted to higher temperatures, such as those encountered at host entry, showed derepressed tlpA activity. tlpA lacZ fusions indicated that the promoter itself...
The Holliday junction recombination intermediate, an X-shaped DNA molecule (xDNA), was analyzed at rDNA in mitotically growing yeast. In wild-type cells, xDNA is only detected at S phase, suggesting that recombination is stimulated to repair replication- related lesions. A search for mutations that increase the level of xDNA uncovered a gene encoding a subunit of DNA polymerase α. Systematic examination...
Hsp90 molecular chaperones in eukaryotic cells play essential roles in the folding and activation of a range of client proteins involved in cell cycle regulation, steroid hormone responsiveness, and signal transduction. The biochemical mechanism of Hsp90 is poorly understood, and the involvement of ATP in particular is controversial. Crystal structures of complexes between the N-terminal domain of...
Distinct classes of motor neurons and ventral interneurons are generated by the graded signaling activity of Sonic hedgehog (Shh). Shh controls neuronal fate by establishing different progenitor cell populations in the ventral neural tube that are defined by the expression of Pax6 and Nkx2.2. Pax6 establishes distinct ventral progenitor cell populations and controls the identity of motor neurons and...
Exposure of E. coli to hydrogen peroxide induces the transcription of a small RNA denoted oxyS. The oxyS RNA is stable, abundant, and does not encode a protein. oxyS activates and represses the expression of numerous genes in E. coli, and eight targets, including genes encoding the transcriptional regulators FhlA and σ s , were identified. oxyS expression also leads to a reduction in spontaneous...
DNA was extracted from the Neandertal-type specimen found in 1856 in western Germany. By sequencing clones from short overlapping PCR products, a hitherto unknown mitochondrial (mt) DNA sequence was determined. Multiple controls indicate that this sequence is endogenous to the fossil. Sequence comparisons with human mtDNA sequences, as well as phylogenetic analyses, show that the Neandertal sequence...
Double-stranded DNA break repair and homologous recombination in E. coli are initiated by the RecBCD enzyme, which unwinds and simultaneously degrades DNA from a double-stranded DNA end. This process is stimulated by cis-acting DNA elements, known as χ sites. Using both in vitro pairing and nuclease protection assays, we demonstrate that the translocating RecBCD enzyme, which has been activated by...
Mutations at the mouse Fused locus have pleiotropic developmental effects, including the formation of axial duplications in homozygous embryos. The product of the Fused locus, Axin, displays similarities to RGS (Regulators of G-Protein Signaling) and Dishevelled proteins. Mutant Fused alleles that cause axial duplications disrupt the major mRNA, suggesting that Axin negatively regulates the response...
The Drosophila melanogaster fuzzy onions (fzo) gene encodes the first known protein mediator of mitochondrial fusion. During Drosophila spermatogenesis, mitochondria in early postmeiotic spermatids aggregate, fuse, and elongate beside the growing flagellar axoneme. fzo mutant males are defective in this developmentally regulated mitochondrial fusion and are sterile. fzo encodes a large, novel, predicted...
The activity of the N-terminal activation function AF-1 of RARα1 is abrogated upon mutation of a phosphorylatable serine residue (Ser77). Recombinant RARα was phosphorylated by a variety of proline-directed protein kinases in vitro. However, only the coexpression of cdk7 stimulated Ser77 phosphorylation in vivo and enhanced transactivation by RARα, but not by a S77A RAR mutant. Both free CAK (cdk7,...
Disorder in sister chromatid separation can lead to genome instability and cancer. A temperature-sensitive S. pombe mis6-302 frequently loses a minichromosome at 26 o C and abolishes equal segregation of regular chromosomes at 36 o C. The mis6 + gene is essential for viability, and its deletion results in missegregation identical to mis6-302. Mis6 acts before or at the onset...
Portions of the nascent chain are exposed to the lumen, the cytosol, or neither at different stages during the cotranslational integration of a protein into the ER membrane, as shown by compartment-specific collisional quenching of fluorophores incorporated into the polypeptide. The opening or closing of each end of the aqueous translocon pore is tightly controlled and occurs in a sequence that does...
Alpha-mannosidase-II (αM-II) catalyzes the first committed step in the biosynthesis of complex asparagine- linked (N-linked) oligosaccharides (N-glycans). Genetic deficiency of αM-II should abolish complex N-glycan production as reportedly does inhibition of αM-II by swainsonine. We find that mice lacking a functional αM-II gene develop a dyserythropoietic anemia concurrent with loss of erythrocyte...
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