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Production of infectious RNA transcripts from full-length cDNA clones representing two subgroups of peanut stunt virus strains: mapping satellite RNA support to RNA1.

Full-length cDNA clones from which infectious transcripts could be generated were constructed from the genomic RNAs of two distinct strains of peanut stunt cucumovirus (PSV), PSV-ER and PSV-W. PSV-ER, a subgroup I strain, is known to support efficient replication of satellite RNA (satRNA) in infected plants, whereas PSV-W, a subgroup II strain, does not support satRNA replication. Although artificial reassortants (pseudorecombinants) of all possible combinations of infectious transcripts representing RNA1, RNA2 and RNA3 were infectious, only those having RNA1 from PSV-ER supported the replication of satRNA. These results demonstrate conclusively that support of PSV satRNA replication maps to RNA1. Comparisons of secondary structure predictions of the C-terminal helicase-like domain of the 1a proteins of four PSV strains belonging to two subgroups did not reveal any obvious differences between strains that differ in satRNA support. The complete nucleotide sequence of RNA1 from strains PSV-ER and PSV-W were determined and found to be 79% identical. Sequence comparison analysis of RNA1 sequences of cucumoviruses confirmed the placement of the PSV strains into two distinct subgroups.

Amino Acid Sequence↗

Rapid determination of short DNA sequences by the use of MALDI-MS.

We have developed a protocol for rapid sequencing of short DNA stretches (15-20 nt) using MALDI-TOF-MS. The protocol is based on the Sanger concept with the modification that double-stranded template DNA is used and all four sequencing reactions are performed in one reaction vial. The sequencing products are separated and detected by MALDI-TOF-MS and the sequence is determined by comparing measured molecular mass differences to expected values. The protocol is optimized for low costs and broad applicability. One reaction typically includes 300 fmol template, 10 pmol primer and 200 pmol each nucleotide monomer. Neither the primer nor any of the nucleotide monomers are labeled. Solid phase purification, concentration and mass spectrometric sample preparation of the sequencing products are accomplished in a few minutes and parallel processing of 96 samples is possible. The mass spectrometric analyses and subsequent sequence read-out require only a few seconds per template.

Alleles↗

cDNA cloning, chromosome assignment, and genomic structure of a human gene encoding a novel member of the RBM family.

We have cloned and characterised a novel human gene mapping to chromosome 20q11.2. A partial transcript was initially isolated from a human cDNA library transcribed from RNA of the colon carcinoma cell line T-84. In order to determine the full coding sequence of this novel mRNA, we isolated seven cDNA clones from a human cDNA library transcribed from RNA of the acute monocytic leukemia cell line THP1 by colony hybridization. On Northern blot analysis of four human cell lines, the cDNAs isolated hybridize with an abundantly expressed mRNA species of 3.5 kb. A full-length cDNA transcript of this novel mRNA has an open reading frame of 2,796 bp encoding a protein with a calculated molecular weight of 97 kDa. Two repetitive structural consensus motifs are contained within the deduced protein sequence, namely five distinct RNA binding motifs and two proline rich regions. The derived protein sequence also contains putative transmembrane domains. These structural motifs identify this novel protein as a member of an expanding protein family containing RNA binding motifs (RBM). As seen from recently completed sequence of the genomic area encoding this novel mRNA by the Sanger Centre Human Genome Project, the coding region of this gene, RBM12, is intronless.

Amino Acid Motifs↗

APEX disease gene resequencing: mutations in exon 7 of the p53 tumor suppressor gene.

Detection of mutations in disease genes will be a significant application of genomic research. Methods for detecting mutations at the single nucleotide level are required in highly mutated genes such as the tumor suppressor p53. Resequencing of an individual patient's DNA by conventional Sanger methods is impractical, calling for novel methods for sequence analysis. Toward this end, an arrayed primer extension (APEX) method for identifying sequence alterations in primary DNA structure was developed. A two-dimensional array of immobilized primers (DNA chip) was fabricated to scan p53 exon 7 by single bases. Primers were immobilized with 200 microm spacing on a glass support. Oligonucleotide templates of length 72 were used to study individual APEX resequencing reactions. A template-dependent DNA polymerase extension was performed on the chip using fluorescein-labeled dideoxynucleotides (ddNTPs). Labeled primers were evanescently excited and the induced fluorescence was imaged by CCD. The average signal-to-noise ratio (S/N) observed was 30:1. Software was developed to analyze high-density DNA chips for sequence alterations. Deletion, insertion, and substitution mutations were detected. APEX can be used to scan for any mutation (up to two-base insertions) in a known region of DNA by fabricating a DNA chip comprising complementary primers addressing each nucleotide in the wild-type sequence. Since APEX is a parallel method for determining DNA sequence, the time required to assay a region is independent of its length. APEX has a high level of accuracy, is sequence-based, and can be miniaturized to analyze a large DNA region with minimal reagents.

DNA Mutational Analysis↗

Report and abstracts of the Sixth International Workshop on chromosome 9.

A meeting on chromosome 9 was held on Tuesday, 27 October 1998 in Denver, with 38 participants (see appendix). Since the last meeting several of the positional cloning efforts on chromosome 9q have come to fruition, and the most detailed discussion was on 9p. Dr Ian Dunham from the Sanger Centre explained the strategy to be used for sequencing chromosome 9, and encouraged collaboration in the preparatory mapping. He indicated that some priority could be given to those regions where people in the field had a strong interest and could identify relevant PAC clones. At this short meeting it was clearly not possible to construct a comprehensive map of chromosome 9, and it was decided that efforts should be made to maintain links to sources of information on the chromosome 9 web page (http:@www.gene.ucl.ac.uk/chr9/). The discussions at the meeting are summarized in four sections: 9p, 9cen-q31, 9q32-9q34 and comparative mapping. Many of the posters presented at the meeting were also presented at the ASHG meeting (28-31 October 1998). They are listed here and are published in The American Journal of Human Genetics, vol. 63 (supplement). Abstracts for posters presented only at this meeting are appended to this report.

Animals↗

[A method of determining the primary structure of oligodeoxyribonucleotides].

Sanger method was modified to fulfill the requirements of sequencing of oligodeoxyribonucleotides. E. coli DNA polymerase I Klenow fragment was used for all the reactions. The method consists of three steps made in succession in one tube: 1. Optional hydrolysis of a 5'-labeled oligodeoxyribonucleotide primer in order to get a set of primers of different lengths. 2. Elongation of the produced set of primers in the presence of a template, natural dNTPs and chain terminating dNTP analogs. 3. Hydrolysis of the products of the previous step in order to remove the unterminated molecules. Change of steps in achieved just by varying the reaction conditions without any product purification. The method in insensitive to the presence of admixture of oligonucleotides which is not complementary to the primer or to the template.

Base Sequence↗

New rapid methods for DNA sequencing based in exonuclease III digestion followed by repair synthesis.

We describe improve enzymatic methods for sequencing method for sequencing DNA. They are based on partial digestion of duplex DNA with exonuclease III to produce DNA molecules with 3' ends shortened to varying lengths, followed by repair synthesis to extend and label the 3' ends. After asymmetrical cleavage of the DNA with a restriction enzyme, the labeled products are separated by gel electrophoresis and the sequence read from the autoradiogram. The entire procedures, beginning with unrestricted DNA and followed through gel electrophoresis, takes only one day for sequencing both strands of the DNA molecule. These methods are especially suitable for sequencing DNA cloned in plasmid vectors, and they greatly extend the usefulness of the dideoxynucleotide chain termination method of Sanger et al. (Proc. Natl. Acad. Sci. USA 74, 5463, 1977). Using these methods we have determined the sequence of a 410 base pair fragment which includes the yeast SUP3 tyrosine tRNA gene.

Base Composition↗

The 3' terminal oligonucleotide of E. coli 16S ribosomal RNA: the sequence in both wild-type and RNase iii- cells is complementary to the polypurine tracts common to mRNA initiator regions.

Application of Sanger techniques to the analysis of the 3' terminal oligonucleotide from E. coli 32-P-labelled 16 S rRNA yields the sequence AUCACCUCCUUAOH. This sequence is identical in RNA isolated from two wild-type strains (MRE600 and E. coli B, SY106) and from a mutant strain (AB301/105) defective in RNase III. Data presented here explains the previous derivation of an incorrect sequence (AUCCUCACUUCAOH) by others. The functional significance of complementarity between the 3' terminus of 16S rRNA and poly-purine tracts commonly found in mRNA initiator regions is discussed.

Base Sequence↗

Reclassification of Treponema hyodysenteriae and Treponema innocens in a new genus, Serpula gen. nov., as Serpula hyodysenteriae comb. nov. and Serpula innocens comb. nov.

The intestinal anaerobic spirochetes Treponema hyodysenteriae B78T (T = type strain), B204, B169, and A-1, Treponema innocens B256T and 4/71, Treponema succinifaciens 6091T, and Treponema bryantii RUS-1T were compared by performing DNA-DNA reassociation experiments, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cell proteins, restriction endonuclease analysis of DNA, and 16S rRNA sequence analysis. DNA-DNA relative reassociation experiments in which the S1 nuclease method was used showed that T. hyodysenteriae B78T and B204 had 93% sequence homology with each other and approximately 40% sequence homology with T. innocens B256T and 4/71. Both T. hyodysenteriae B78T and T. innocens B256T exhibited negligible levels of DNA homology (less than or equal to 5%) with T. succinifaciens 6091T. The results of comparisons of protein electrophoretic profiles corroborated the DNA-DNA reassociation results. We found high levels of similarity (greater than or equal to 96%) in electrophoretic profiles among T. hyodysenteriae strains, moderate levels of similarity (43 to 49%) between T. hyodysenteriae and T. innocens, and no detectable similarity between the profiles of either T. hyodysenteriae or T. innocens and those of T. succinifaciens, T. bryantii, and Escherichia coli. Restriction endonuclease analysis of DNA was not useful in assessing genetic relationships since there was heterogeneity even between strains of T. hyodysenteriae. Partial 16S rRNA sequences of the intestinal spirochetes were determined by using a modified Sanger method and were compared in order to evaluate the phylogenetic relationships among these and other spirochetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗

Sequence analysis of the DNA encoding the Eco RI endonuclease and methylase.

The Eco RI endonuclease and methylase recognize the same hexanucleotide substrate sequence. We have determined the sequence of a fragment of DNA which encodes these enzymes using the chain-termination method of Sanger (Sanger, F., Nicklen, S., and Coulson, A. R. (1977) Proc. Natl. Acad. Sci. U. S. A. 74, 5463-5467). The amino acid sequences of both enzymes were derived from the DNA sequence. The coding regions selected include the only open translational frames of sufficient length to accommodate the enzymes. They coincide with previously established gene boundaries and orientation. The predicted amino acid sequences correlate well with analyses of the purified protein. Comparison of the nucleotide and protein sequences reveals no homology between the endonuclease and methylase which might provide insight into the origin of the restriction-modification system or the mechanism of common substrate recognition. Based on secondary structure predictions, the two enzymes also have grossly different molecular architecture. The base composition of the sequence is 65% A + T, and the codon usage is significantly different from that observed in several Escherichia coli chromosomal genes. In some cases, frequently selected codons are recognized by minor tRNA species. A spontaneous mutation in the endonuclease gene was isolated. Serine replaces arginine at residue 187. In crude extracts, Eco RI specific cleavage is approximately 0.3% wild type.

Amino Acid Sequence↗

Amorphin is phosphorylase; phosphorylase is an alpha-actinin-binding protein.

In a study of myofibrillar proteins, Chowrashi and Pepe [1982: J. Cell Biol. 94:565-573] reported the isolation of a new, 85-kD Z-band protein that they named amorphin. We report that partial sequences of purified amorphin protein indicate that amorphin is identical to phosphorylase, an enzyme important in the metabolism of glycogen. Anti-amorphin antibodies also reacted with purified chicken and rabbit phosphorylase. To explore the basis for phosphorylase's (amorphin's) localization in the Z-bands of skeletal muscles, we reacted biotinylated alpha-actinin with purified amorphin and with purified phosphorylase and found that alpha-actinin bound to each. Radioimmune assays also indicated that phosphorylase (amorphin) bound to alpha-actinin, and, with lower affinity, to F-actin. Negative staining of actin filaments demonstrated that alpha-actinin mediates the binding of phosphorylase to actin filaments. There are several glycolytic enzymes that bind actin (e.g., aldolase, phosphofructokinase, and pyruvate kinase), but phosphorylase is the first one demonstrated to bind alpha-actinin. Localization of phosphorylase in live cells was assessed by transfecting cultures of quail embryonic myotubes with plasmids expressing phosphorylase fused to Green Fluorescent Protein (GFP). This resulted in targeting of the fusion protein to Z-bands accompanied by a diffuse pattern in the cytoplasm.

Actinin↗