Sequence-independent RNA cleavages generate the primers for plus strand DNA synthesis in hepatitis B viruses: implications for other reverse transcribing elements.

Reverse transcription of RNA into duplex DNA requires accurate initiation of both minus and plus strand DNA synthesis; this in turn requires the generation of specific primer molecules. We have examined plus strand primer generation in the hepatitis B viruses, small DNA viruses that replicate via reverse transcription. The plus strand primer in these viruses is a short capped RNA derived from the 5' end of the RNA template by cleavage at a specific set of sites.

The trk proto-oncogene rescues NGF responsiveness in mutant NGF-nonresponsive PC12 cell lines.

The trk tyrosine kinase proto-oncogene product gp140prototrk binds nerve growth factor (NGF) and is rapidly and selectively activated by this neurotrophic factor. To determine whether gp140prototrk is involved in transducing a functional NGF signal, PC12 cell mutants (PC12nnr) deficient in high affinity NGF binding and unresponsive to NGF were used. Northern analysis revealed that these mutant cells have greatly reduced levels of trk expression.

L1 gene conversion or same-site transposition.

DNA sequence analysis of the same chromosomal region from two haplotypes of Mus musculus and from the related species M. caroli and M. pahari reveals the presence of long interspersed sequence one (LINES-1, or L1) elements residing at the same nucleotide position in the two most distantly related of the species (M.

Analysis of retroviral protease cleavage sites reveals two types of cleavage sites and the structural requirements of the P1 amino acid.

Retroviruses encode a protease which cleaves the viral Gag and Gag/Pol protein precursors into mature products. To understand the target sequence specificity of the viral protease, the amino acid sequences from 46 known processing sites from 10 diverse retroviruses were compared. Sequence preference was evident in positions P4 through P3' when compared to flanking sequences.

cis-acting sequences required for encapsidation of duck hepatitis B virus pregenomic RNA.

Hepadnavirus reverse transcription requires that pregenomic RNA first be selectively packaged into a cytoplasmic core particle. This process presumably requires the presence of specific recognition sequences on the pregenomic RNA. To define the cis-acting sequences required for pregenome encapsidation in the duck hepatitis B virus (DHBV), we assayed the packaging efficiency of a series of pregenomic RNA deletion mutants and hybrid DHBV/lacZ fusion transcripts.

Subject case marking and verb morphology in normally developing and specifically language-impaired children.

Recent theories of language development propose a direct relationship between children's use of verb morphology and their use of subject case pronouns. Such proposals might contribute to an understanding of specifically language-impaired (SLI) children's difficulties. These children's extraordinary problems with verb morphology are well documented, and preliminary evidence indicates frequent pronoun case errors (e.

Mutations affecting hepadnavirus plus-strand DNA synthesis dissociate primer cleavage from translocation and reveal the origin of linear viral DNA.

Hepadnaviruses replicate their circular DNA genomes via reverse transcription of an RNA intermediate. The initial product of reverse transcription, minus-strand DNA, contains two copies of a short direct repeat (DR) sequence, termed DR1 and DR2. Plus-strand DNA synthesis initiates at DR2 on minus-strand DNA, using as a primer a short, DR1-containing oligoribonucleotide derived by cleavage and translocation from the 5' end of pregenomic RNA.

Plasmid origin of replication of herpesvirus papio: DNA sequence and enhancer function.

Herpesvirus papio (HVP) is a lymphotropic virus of baboons which is related to Epstein-Barr virus (EBV) and produces latent infection. The nucleotide sequence of the 5,775-base-pair (bp) EcoRI K fragment of HVP, which has previously been shown to confer the ability to replicate autonomously, has been determined. Within this DNA fragment is a region which bears structural and sequence similarity to the ori-P region of EBV.

Cleavage of HIV-1 gag polyprotein synthesized in vitro: sequential cleavage by the viral protease.

The virally encoded protease of human immunodeficiency virus is responsible for the processing of the gag and gag-pol polyprotein precursors to their mature polypeptides. Since correct processing of the viral polypeptides is essential for the production of infectious virus, HIV protease represents a potential target for therapeutic agents that may prove beneficial in the treatment of AIDS. In this study, full-length gag polyprotein has been synthesized in vitro to serve as a substrate for bacterially expressed HIV-1 protease.

Differential inhibition of nerve growth factor responses by purine analogues: correlation with inhibition of a nerve growth factor-activated protein kinase.

Purine analogues were used in this study to dissect specific steps in the mechanism of action of nerve growth factor (NGF). Protein kinase N (PKN) is an NGF-activated serine protein kinase that is active in the presence of Mn++. The activity of PKN was inhibited in vitro by purine analogues, the most effective of which was 6-thioguanine (apparent Ki = 6 microM).

Unusual phonological behavior and the avoidance of homonymy in children.

Young children sometimes make use of unusual phonological patterns even when they already possess the appropriate sound or a suitable substitute in their phonological systems. In this investigation, we attempted to determine whether in such instances unusual sound changes enable children to avoid potential homonymy with other words in their lexicons. Novel words were presented to children, half serving as potential homonyms, half as unlikely homonyms.

Complete mutagenesis of the HIV-1 protease.

Retroviruses encode a protease which needs to be active for the production of infectious virions. A disabling mutation in the protease results in the production of non-infectious virus particles and examination of proteins from these mutant virions reveals unprocessed Gag and Gag-Pol precursor proteins, the substrates of the viral protease. Each amino acid of the HIV-1 protease was individually mutated using a simple mutagenesis procedure which is capable of introducing and identifying missense mutations in each residue of a protein.

Nucleotide sequence of the BALB/c mouse beta-globin complex.

The nucleotide sequence of 55,856 base-pairs containing all seven beta-globin homologous structures from chromosome 7 of the BALB/c mouse is reported. This sequence links together previously published sequences of the beta-globin genes, pseudogenes and repetitive elements. Using low stringency computer searches, we found no additional beta-globin homologous sequences, but did find many more long interspersed repetitive sequences (L1) than predicted by hybridization.

Mutational analysis of human immunodeficiency virus type 1 protease suggests functional homology with aspartic proteinases.

Processing of the retroviral gag and pol gene products is mediated by a viral protease. Bacterial expression systems have been developed which permit genetic analysis of the human immunodeficiency virus type 1 protease as measured by cleavage of the pol protein precursor. Deletion analysis of the pol reading frame locates the sequences required to encode a protein with appropriate proteolytic activity near the left end of the pol reading frame but largely outside the gag-pol overlap region, which is at the extreme left end of pol.

Government-Binding Theory and some of its applications: a tutorial.

Government-Binding Theory is the dominant theory of grammar in present-day linguistics, and is receiving increasing attention from investigators of normal and disordered language behavior. This paper serves as a general introduction to the theory and provides a number of examples of its application.

A directed nucleotide-sequencing approach for single-stranded vectors based on recloning intermediates of a progressive DNA synthesis reaction.

A simple method for site-directed nucleotide sequencing is presented that uses a novel procedure for generating nested 'deletions' within inserts of single-stranded clones. In this method, single-stranded template, sequencing primer, and the Klenow fragment of Escherichia coli DNA polymerase I are used to initiate progressive DNA synthesis of the entire insert of the clone. By time-dependent sampling and pooling of intermediates from the synthesis reaction a series of nested double-stranded DNA subfragments of the insert can be created.

Determination of a functional ancestral sequence and definition of the 5' end of A-type mouse L1 elements.

The complete nucleotide sequence of L1Md-A13, a 6372 base-pair (bp) member of the L1Md repetitive family isolated from a BALB/c mouse genomic DNA library, is reported. The nucleotide sequence of 4331 bp from the 5' end of L1Md-9, which is located in the beta-globin complex of the C57BL/10 mouse, is also reported. Parsimony analysis of these sequences plus two previously reported L1Md sequences allows the determination of an ancestral L1Md sequence.

pp60c-src has less affinity for the detergent-insoluble cellular matrix than do pp60v-src and other viral protein-tyrosine kinases.

A difference in affinity for a Nonidet P-40-insoluble cellular matrix was observed between the products of the viral and cellular src genes. It has previously been demonstrated that pp60v-src is associated with a detergent-insoluble matrix containing the cellular cytoskeleton (J. G.

Expression and processing of the AIDS virus reverse transcriptase in Escherichia coli.

The ability to express the genes of pathogenic human viruses, such as the acquired immune deficiency syndrome (AIDS) virus (also called human immunodeficiency virus) in bacterial cells affords the opportunity to study proteins that are ordinarily difficult or inconvenient to obtain in amounts sufficient for detailed analysis. A segment of the AIDS virus pol gene was expressed in Escherichia coli. Expression resulted in the appearance of reverse transcriptase activity in the bacterial cell extracts.

The molecular organization of the beta-globin complex of the deer mouse, Peromyscus maniculatus.

Recombinant DNA clones have been isolated that contain 80 kb of the beta-globin complex from the deer mouse, Peromyscus maniculatus. Comparisons of this complex with that from the laboratory mouse, Mus domesticus (with an order 5'-Hbby, Hbb-bhO, Hbb-bhl, Hbb-bh2, Hbb-bh3, Hbb-bl, Hbb-b2 3') highlight organizational trends in the beta-globin complex since the two species diverged. Unlike other mammals studied thus far, the deer mouse possesses three adult genes.

Puerperal Pasteurella multocida septicemia.

A case of Pasteurella multocida infection in a puerperal healthy young women is reported. The agent was isolated from vaginal discharge and blood cultures of the patient, and also from pets and poultry with which the patient was in contact. Although Pasteurella multocida septicemia is rare, awareness of this infection and adequate intensive antibiotic therapy may improve its prognosis.