Isolation and characterization of the mouse metallothionein-I gene.

Double-stranded cDNA was synthesized from a mouse liver mRNA fraction enriched for metallothionein mRNA activity, ligated to restriction site linkers, inserted into pBR322, and used to transform Escherichia coli chi 1776. The sequence of the largest plasmid containing DNA that hybridized to metallothionein mRNA was determined and shown to contain a 380-base-pair insert that includes the entire coding region and 3' untranslated region of metallothionein-I. The metallothionein-I insert was nick-translated and used to screen both a mouse myeloma and a mouse embryo DNA library in bacteriophage lambda. A metallothionein-I genomic clone containing 13-15 kilobase pairs of mouse DNA was isolated from each library. Both contain a 3.8-kilobase-pair EcoRI fragment that hybridizes to the metallothionein-I probe. The location, size, and orientation of the metallothionein-I gene within the 3.8-kilobase-pair fragment were determined by heteroduplex and restriction mapping. The gene spans 1.1 kilobase pairs and contains at least two introns.     

Bacillus stearothermophilus contains a plasmid-borne gene for alpha-amylase.

The gene for thermostable alpha-amylase from the thermophilic bacterium Bacillus stearothermophilus has been cloned and expressed in Escherichia coli. Each alpha-amylase-producing colony contained at least a 9.7-kilobase-pair (kb) chimeric plasmid composed of the vector pBR322 and a common 5.4-kb HindIII fragment of DNA. B. stearothermophilus contains four plasmids with sizes from 12 kb to over 108 kb. Restriction endonuclease analysis of these naturally occurring plasmids showed they also contain a 5.4-kb HindIII fragment of DNA. Cloning experiments with the four plasmids yielded alpha-amylase-producing E. coli that contained the same 9.7-kb chimeric plasmid. Restriction endonuclease analysis and further recombinant DNA experiments identified a 26-kb plasmid that contains the gene for alpha-amylase. A spontaneous mutant of B. stearothermophilus unable to produce alpha-amylase was missing the 26-kb plasmid but contained a 20-kb plasmid. A 6-kb deletion within the region of the 5.4-kb HindIII fragment yielded the 20-kb plasmid unable to code for alpha-amylase. A nick-translated probe for the alpha-amylase coding region did not hybridize to either plasmid or total cellular DNA from this mutant strain of B. stearothermophilus. These results demonstrate the gene for alpha-amylase is located exclusively on a 26-kb plasmid in B. stearothermophilus with no genetic counterpart present on the chromosome.     

Structure and function of a chloroplast DNA replication origin of Chlamydomonas reinhardtii

Chloroplast DNA replication in Chlamydomonas reinhardtii is initiated by the formation of a displacement loop (D-loop) at a specific site. One D-loop site with its flanking sequence was cloned in recombinant plasmids SC3-1 and R-13. The sequence of the chloroplast DNA insert in SC3-1, which includes the 0.42-kilobase (kb) D-loop region, as well as 0.2 kb to the 5′ end and 0.43 kb to the 3′ end of the D-loop region, was determined. The sequence is A+T-rich and contains four large stem-loop stuctures. An open reading frame potentially coding for a polypeptide of 136 amino acids was detected in the D-loop region. One stem-loop structure and two back-to-back prokaryotic-type promoters were mapped within the open reading frame. The 5.5-kb EcoRI fragment cloned in R-13 contains the 1.05-kb SC3-1 insert and its flanking regions. A yeast autonomously replicating (ARS) sequence and an ARC sequence, which promotes autonomous replication in Chlamydomonas, have been mapped within the flanking regions [Vallet, J.-M. & Rochaix, J.-D. (1985) Curr. Genet. 9, 321-324]. Both R-13 and SC3-1 were active as templates in a crude algal preparation that supports DNA synthesis. In this in vitro system, chloroplast DNA synthesis initiated near the D-loop site.     

Isolation and sequence determination of a cDNA clone for rat peroxisomal urate oxidase: liver-specific expression in the rat.

Urate oxidase (UOxase; urate:oxygen oxidoreductase, EC 1.7.3.3), which catalyzes the oxidation of uric acid to allantoin, is present in most mammals but is absent in humans and certain primates. A cDNA clone for UOxase containing an insert of 1.3 kilobases (kb) was isolated from a lambda gt11 cDNA library prepared from rat liver mRNA. This recombinant clone with a 1283-nucleotide insert has sequence for 97% of the coding region together with 401 nucleotides of the 3'-untranslated region of the mRNA. The identity of UOxase cDNA clone was verified by analyzing the fusion protein, immunocytochemical localization with epitope-selected antibody, and hybrid-select translation analysis and by comparing sequences of four CNBr-cleaved peptides of the protein. Blot analysis revealed that the probe hybridizes to a single 1.5-kb mRNA species in the rat liver and a transplantable hepatocellular carcinoma. No UOxase mRNA was detected in 11 nonhepatic tissues of rat, suggesting tissue specificity of expression of this UOxase gene. Blot analysis of RNA from livers of rats treated with a peroxisome proliferator showed 2- to 3-fold increase in UOxase mRNA content, whereas the fatty acyl-CoA oxidase mRNA increased over 30-fold. Southern blot analysis of restriction enzyme digests of rat DNA suggests that there is a single copy of UOxase gene. Analysis of human genomic DNA revealed restriction fragments that are homologous to rat UOxase cDNA, although no UOxase mRNA was detected in human liver.     

Cloning and nucleotide sequence of DNA coding for bovine preproparathyroid hormone.

We have cloned in Escherichia coli a DNA copy of mRNA coding for bovine preproparathyroid hormone. Double-stranded DNA was inserted into the Pst I site in plasmid pBR322 by using the poly(dG)-poly(dC) homopolymer extension technique to join the DNA molecules. Recombinant plasmids coding for preproparathyroid hormone were identified by the plasmid's ability to arrest specifically the translation of preproparathyroid hormone mRNA. The nucleotide sequence of the largest recombinant was determined by using both chemical and enzymatic techniques. The parathyroid insert contains 470 nucleotides--102 nucleotides from the 5' noncoding region of the mRNA, 345 nucleotides representing the entire coding region, and 23 nucleotides from the 3' noncoding region. The coding sequence clarifies the hormone's amino acid sequence, which has been disputed. Codon usage is discussed.     

Structure of genes for human growth hormone and chorionic somatomammotropin.

A 2.6-kilobase (kb) EcoRI restriction endonuclease fragment containing human growth hormone (hGH; somatotropin) gene sequences and a 2.8-kb EcoRI fragment containing human chorionic somatomammotropin (hCS; choriomammotropin) gene sequences have been identified by hybridization to cloned cDNA. Human DNA was cleaved with EcoRI and fractionated by preparative agarose gel electrophoresis; DNA in the size range 2--3 kb was ligated to lambda gt WES.lambda B DNA and viable recombinant bacteriophage were recovered by in vitro packaging. After infection of Escherichia coli and screening of phage plaques, single isolates of hGH and hCS gene sequences were obtained. Restriction endonuclease mapping showed that the hGH gene contains three intervening sequences interrupting the coding sequence. Partial DNA sequence analysis of the hGH gene, obtained by the chain termination method, confirmed the location of the intervening sequences and the identity of the fragment.     

Evolution and assembly of an extremely scrambled gene

The process of gene unscrambling in hypotrichous ciliates represents one of nature's ingenious solutions to the problem of gene assembly. With some essential genes scrambled in as many as 51 pieces, these ciliates rely on sequence and structural cues to rebuild their fragmented genes and genomes. Here we report the complex pattern of scrambling in the DNA polymerase alpha gene of Stylonychia lemnae. The germline (micronuclear) copy of this gene is broken into 48 pieces with 47 dispersed over two loci, with no asymmetry in the placement of coding segments on either strand. Direct repeats present at the boundaries between coding and noncoding sequences provide pointers to help guide assembly of the functional (macronuclear) gene. We investigate the evolution of this complex gene in three hypotrichous species.     

Mutated beta-actin gene: coexpression with an unmutated allele in a chemically transformed human fibroblast cell line.

By in vitro translation, we have identified the mRNA species that codes for a novel actin polypeptide (Ax-actin) in the chemically transformed human fibroblast line HuT-14. The relatedness of the coding sequences of the Ax- and beta-actin genes is indicated by our finding that pcDd actin ITL-I DNA, a recombinant plasmid DNA that contains a DNA sequence complementary to actin mRNA of Dictyostelium discoideum, hybridizes both the Ax-actin mRNA and the beta-actin mRNA but not the gamma-actin mRNA. In contrast, pcHa-1 DNA, a recombinant plasmid constructed by cloning a DNA sequence complementary to human actin mRNA from HuT-14 cells into pBR322, hybridized to all three mRNA species. In addition, no difference was observed between Ax- and beta-actin mRNAs when their molecular size was determined either by sucrose density gradient sedimentation or by methyl mercury agarose gel electrophoresis. Southern blot transfer of radioactive pcDd actin DNA to restriction endonuclease-digested Hut-14 DNA produced only a single hybrid band (a 6-kilobase fragment); the pcHa-1 DNA probe detected one additional band (a 3-kilobase fragment). These results suggest that HuT-14 cells contain only one copy per haploid genome for Ax- or beta-actin. When considered together with recent determination of the entire amino acid sequences of Ax- and beta-actin, our findings indicate that Ax-actin is the product of a mutated beta-actin gene and are evidence for the occurrence of a mutation in a chemically transformed cell.     

Molecular cloning and expression of the imipenem-hydrolyzing beta-lactamase gene from Pseudomonas maltophilia in Escherichia coli

The L-1 penicillinase structural gene, blaS, from Pseudomonas maltophilia was cloned into the vector pACYC184. The pMON01 recombinant plasmid selected by ampicillin resistance carried a 2.6-kilobase (kb) Sau3A fragment of P. maltophilia DNA and was confirmed to express L-1 beta-lactamase by comparative isoelectric focusing. A detailed physical map was constructed, and the blaS structural gene was localized with a 17-mer oligonucleotide mixed probe encoding the L-1 NH2-terminal amino acid sequence. Induction studies confirmed constitutive expression. Isolation of a complete beta-lactamase operon was attempted by construction of a P. maltophilia genomic library into phage lambda 2001. A recombinant phage was selected by DNA hybridization; the 13.4-kb DNA insert was physically mapped and subcloned into the high-copy-number plasmid pACYC184 and into the low-copy-number vector pLG338. The expression of the cloned blaS L-1 structural gene and levels of beta-lactamase synthesis were studied in Escherichia coli. The protein synthesized was found to be similar to the L-1 beta-lactamase of the prototype P. maltophilia, although expression levels were gene dosage dependent for beta-lactamase synthesis.     

Isolation and sequence of the gene for actin in Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae is known to contain the highly conserved and unbiquitous protein actin. We have used cloned actin sequences from Dictyostelium discoideum to identify and clone the actin gene in yeast. Hybridization to genomic fragments of yeast DNA suggest that there is a single actin gene in yeast. We have determined the nucleotide sequence of that gene and its flanking regions. The sequence of the gene reveals an intervening sequence of 309 base pairs in the coding sequences at the 5' end of the gene. The existence and location of the intervening sequence was verified by using the dideoxy chain termination technique to determine the sequence at the 5' terminus of the actin mRNA. The similarity of the splice junction sequences in this gene to those found in higher eukaryotes suggests that yeast must possess a similar splicing enzyme.     

Intracisternal A-particle genes: identification in the genome of Mus musculus and comparison of multiple isolates from a mouse gene library.

The genome of Mus musculus contains multiple copies (500 -1000) of DNA sequences related to the 35S RNA of intracisternal type A particles (IAPs). Using labeled IAP RNA as a probe in blot-hybridization experiments, we have identified a characteristic electrophoretic pattern of reactive fragments generated by restriction endonuclease cleavage of mouse DNA. From the genomic blots, we deduced a composite restriction map for a 6.5- to 7-kilobase (kb) DNA region containing sequences homologous to the IAP RNA. Units of this type appeared to be interspersed without obvious regularity in nonhomologous flanking regions. A 5.2-kb segment of this unit was inserted directly into plasmid pBR322 from HindIII/EcoRI digest of mouse DNA. The fragment was cloned and then labeled by nick-translation and used to scan a mouse embryo gene library (average 16-kb inserts in lambda Charon 4A); 1% of the library samples hybridized, confirming the extensive reiteration of IAP genetic units. Among six different library isolates containing 6.5- to 7-kb IAP units, some restriction sites were highly conserved whereas others varied in both occurrence and position. Despite this variation, heteroduplexes between the individual isolates showed continuous IAP homology regions of 7 kb. No flanking region homologies were seen in this limited sample. Some evidence suggests that mouse DNA may contain other dispersed sequence elements related to but smaller than the genetic unit defined above.     

日本血吸虫组织蛋白酶L1基因的编码区全序列分析及克隆

目的 分析日本血吸虫组织蛋白酶L1(SjCL1)基因编码区的完整序列,并定向克隆到真核表达质粒pcD-NA3中。 方法 从日本血吸虫成虫提取总RNA,进行反向巢式RT-PCR,T载体克隆后测序。PCR扩增SjCL1基因的编码区序列,并将扩增产物克隆到pcDNA3质粒的BamHI和Xhol位点上。结果 通过反向巢式RT-PCR扩增出332 bp SjCL1基因5’端序列,测序后与报道的SiCL1基因部分序列拼接,可得到一个编码317个氨基酸的完整编码区序列。PCR特异性扩增出SjCL1编码区基因序列,其大小约为1 kb。经酶切、PCR鉴定和测序表明所构建的质粒pcDNA-SjCL1中含有所扩增的基因序列。 结论 构建了含SjCL1基因的编码区序列的真核表达质粒pcDNA-SjCL1。     

Cloning of yeast TOP1, the gene encoding DNA topoisomerase I, and construction of mutants defective in both DNA topoisomerase I and DNA topoisomerase II.

Rabbit antibodies specific to yeast DNA topoisomerase I were used in immunological screening of a Saccharomyces cerevisiae genomic DNA library in Escherichia coli. One of the clones identified by its expression of antigenic determinants of the yeast enzyme is shown to contain the coding sequence of the enzyme: no active DNA topoisomerase I is detectable in cell extracts when insertion or deletion mutations are introduced into a 2-kilobase-pair (kb) region of the sequence in a haploid yeast genome. Blot hybridizations show that there is a single copy of the cloned sequence per haploid and that the sequence is transcribed to give a 2.7-kb poly(A)+ message. Mutants in which 1.7 kb of the sequence is deleted are viable. Temperature-shift experiments using synchronously grown cells of a delta top1 top2 temperature-sensitive (ts) double mutant and its isogenic top2 ts strain show that, whereas mitotic blocks can prevent killing of the top2 ts mutant at a nonpermissive temperature, the same treatments are ineffective in preventing cell death of the delta top1 top2 ts double mutant. These experiments suggest that in yeast DNA topoisomerase I serves a role auxiliary to DNA topoisomerase II.     

Construction of recombinant plasmids containing rat muscle actin and myosin light chain DNA sequences.

The construction and partial characterization of recombinant bacterial plasmids carrying DNA sequences that hybridize with rat skeletal muscle actin and a myosin light chain mRNA is described. DNA of one clone hybridizes specifically with the muscle-specific alpha-actin mRNA. Three plasmid clones contain DNA inserts that hybridize with muscle as well as with nonmuscle actin mRNA. A fifth plasmid contains sequences complementary to mRNA coding for myosin light chain 2. DNA of this plasmid hybridizes specifically with RNA extracted from muscle and differentiated muscle cultures but not with RNA extracted from proliferating mononucleated myogenic cells.