Expression of the murine Duchenne muscular dystrophy gene in muscle and brain

Complementary DNA clones were isolated that represent the 5' terminal 2.5 kilobases of the murine Duchenne muscular dystrophy (Dmd) messenger RNA (mRNA). Mouse Dmd mRNA was detectable in skeletal and cardiac muscle and at a level approximately 90 percent lower in brain. Dmd mRNA is also present, but at much lower than normal levels, in both the muscle and brain of three different strains of dystrophic mdx mice. The identification of Dmd mRNA in brain raises the possibility of a relation between human Duchenne muscular dystrophy (DMD) gene expression and the mental retardation found in some DMD males. These results also provide evidence that the mdx mutations are allelic variants of mouse Dmd gene mutations.     

Duchenne muscular dystrophy gene expression in normal and diseased human muscle

A probe for the 5' end of the Duchenne muscular dystrophy (DMD) gene was used to study expression of the gene in normal human muscle, myogenic cell cultures, and muscle from patients with DMD. Expression was found in RNA from normal fetal muscle, adult cardiac and skeletal muscle, and cultured muscle after myoblast fusion. In DMD muscle, expression of this portion of the gene was also revealed by in situ RNA hybridization, particularly in regenerating muscle fibers.     

Frame-shift deletions in patients with Duchenne and Becker muscular dystrophy

Duchenne muscular dystrophy (DMD) and its less severe form Becker muscular dystrophy (BMD) are allelic disorders. It has been suggested that in the mutations involving BMD, the translational reading frame of messenger RNA is maintained and a smaller, though partially functional, protein is produced. In order to test this, the exon-intron boundaries of the first ten exons of the DMD gene were determined, and 29 patients were analyzed. In a number of BMD patients (mild and severe BMD), the reading frame of messenger RNA was not maintained. On the basis of these findings, a model for reinitiation from an internal start codon is suggested.     

Increasing the multiplicity of ribosomal RNA genes in Drosophila melanogaster

In wild-type Drosophila melanogaster females there are about 250 ribosomal RNA genes in each nucleolus organizer region of the two X chromosomes. When this same nucleolus organizer region is present in flies in only a single dose, the number of ribosomal RNA genes increases to approximately 400. This increase is most easily explained by disproportionate replication of these genes.     

Molecular analysis of a constitutional X-autosome translocation in a female with muscular dystrophy

The gene responsible for Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) maps to the X chromosome short arm, band Xp21. In a few females with DMD or BMD, the Xp21 region is disrupted by an X-autosome translocation. Accumulating evidence suggests that the exchange has physically disrupted the DMD/BMD locus to cause the disease. One affected female with a t(X;21)(p21;p12) translocation was studied in detail. The exchange points from both translocation chromosomes were cloned, restriction-mapped, and sequenced. The translocation is reciprocal, but not conservative. A small amount of DNA is missing from the translocated chromosomes; 71 to 72 base pairs from the X chromosome and 16 to 23 base pairs from the 28S ribosomal gene on chromosome 21.     

A new probe for the diagnosis of myotonic muscular dystrophy

Myotonic muscular dystrophy (DM) is the most common muscular dystrophy, affecting adults as well as children. It is inherited as an autosomal dominant trait and is characterized by variable expressivity and late age-of-onset. Linkage studies have established the locus on chromosome 19. In order to identify tightly linked probes for diagnosis as well as to define in detail the DM gene region, chromosome 19 libraries were constructed and screened for restriction fragment length polymorphisms tightly linked to DM. A genomic clone, LDR152 (D19S19), was isolated that is tightly linked to DM; recombination fraction = 0.0 (95% confidence limits 0.0-0.03); lod score, 15.4.     

Cytochemical localization of lactate dehydrogenase in muscular dystrophy of the mouse

By use of phenazine methosulfate and the "ncubation mixture film method," lactate dehydrogenase activity has been demonstrated in the dystrophic muscle fibers of strain 129 mice. The results indicate that for demonstration of lactate dehydrogenase activity in dystrophic muscle fibers phenazine methosulfate is necessary. This finding is typical for the "white" muscle fibers in the normal muscle and suggests that the dystrophy affects primarily the "white" muscle fibers.     

棉花疫病菌和辣椒疫病菌核糖体基因ITS区域的克隆和序列分析

采用真菌核糖体基因转录间隔区域（ＩＴＳ）通用引物,ＰＣＲ扩增棉花疫病菌、辣椒疫病菌核糖体基因的ＩＴＳ１和ＩＴＳ２,并对ＰＣＲ产物进行了克隆和序列比较。结果表明：棉花疫病菌的ＩＴＳ１和ＩＴＳ２分别由２０６和４５３个碱基组成,而辣椒疫病菌则分别由１７４和４３２个碱基组成。棉花疫病菌两个菌株之间ＩＴＳ１和ＩＴＳ２的同源性均高达１００％,而棉花疫病菌和辣椒疫病菌ＩＴＳ１同源性为７０．９％,其中中间区域５２     

Turnover of ribosomal RNA in rat liver

After a single injection of radioactive orotic acid and a "chase" of nonradioactive precursor, the specific activity of ribosomal RNA in rat liver decreases logarithmically at a rate corresponding to a half-life of about S days. The possible significance of this result is discussed with regard to control of protein synthesis.     

Secondary structure of 16S ribosomal RNA

A secondary structure model for 16S ribosomal RNA which is based on available chemical, enzymatic, and comparative sequence data shows good agreement between constraints dictated by the model and a wide variety of experimental observations. The four major structural domains created by the base-pairing scheme correspond closely to RNA fragments isolated after nuclease digestion in the presence of bound ribosomal proteins. Functionally important sites appear to be located in unpaired regions and are phylogenetically highly conserved.     

Coupling of Tetrahymena ribosomal RNA splicing to beta-galactosidase expression in Escherichia coli

Splicing of the Tetrahymena ribosomal RNA precursor is mediated by the folded structure of the RNA molecule and therefore occurs in the absence of any protein in vitro. The Tetrahymena intervening sequence (IVS) has been inserted into the gene for the alpha-donor fragment of beta-galactosidase in a recombinant plasmid. Production of functional beta-galactosidase is dependent on RNA splicing in vivo in Escherichia coli. Thus RNA self-splicing can occur at a rate sufficient to support gene expression in a prokaryote, despite the likely presence of ribosomes on the nascent RNA. The beta-galactosidase messenger RNA splicing system provides a useful method for screening for splicing-defective mutations, several of which have been characterized.     

Distribution of protein and RNA in the 30S ribosomal subunit

In Escherichia coli, the small ribosomal subunit has a sedimentation coefficient of 30S, and consists of a 16S RNA molecule of 1541 nucleotides complexed with 21 proteins. Over the last few years, a controversy has emerged regarding the spatial distribution of RNA and protein in the 30S subunit. Contrast variation with neutron scattering was used to suggest that the RNA was located in a central core of the subunit and the proteins mainly in the periphery, with virtually no separation between the centers of mass of protein and RNA. However, these findings are incompatible with the results of efforts to locate individual ribosomal proteins by immune electron microscopy and triangulation with interprotein distance measurements. The conflict between these two views is resolved in this report of small-angle neutron scattering measurements on 30S subunits with and without protein S1, and on subunits reconstituted from deuterated 16S RNA and unlabeled proteins. The results show that (i) the proteins and RNA are intermingled, with neither component dominating at the core or the periphery, and (ii) the spatial distribution of protein and RNA is asymmetrical, with a separation between their centers of mass of about 25 angstroms.     

Recognition of cognate transfer RNA by the 30S ribosomal subunit

Crystal structures of the 30S ribosomal subunit in complex with messenger RNA and cognate transfer RNA in the A site, both in the presence and absence of the antibiotic paromomycin, have been solved at between 3.1 and 3.3 angstroms resolution. Cognate transfer RNA (tRNA) binding induces global domain movements of the 30S subunit and changes in the conformation of the universally conserved and essential bases A1492, A1493, and G530 of 16S RNA. These bases interact intimately with the minor groove of the first two base pairs between the codon and anticodon, thus sensing Watson-Crick base-pairing geometry and discriminating against near-cognate tRNA. The third, or "wobble," position of the codon is free to accommodate certain noncanonical base pairs. By partially inducing these structural changes, paromomycin facilitates binding of near-cognate tRNAs.