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J Rohozinski

Publications and source records attributed to J Rohozinski.

12 recordsLinked to original sources
PubMed2001

Identification and sequencing the juvenile spermatogonial depletion critical interval on mouse chromosome 1 reveals the presence of eight candidate genes.

In mice, the recessive, non-pleiotropic, juvenile spermatogonial depletion (jsd) mutation results in a single wave of spermatogenesis, followed by failure of type A spermatogonial stem cells to differentiate, rendering adult males sterile. As part of an effort to identify the gene underlying this mutation, we report here the construction of a high-resolution genetic map involving more than 1000 meioses and 24 polymorphic loci. Our data define a critical jsd interval of approximately 0.4 cM at 49 cM on mouse chromosome 1, between D1Mit215 and 257SP6. We have constructed a physical map spanning the region comprising 24 overlapping BACs. Eighteen of these BACs have been fully sequenced, or are in draft form, allowing us to annotate approximately 2.5 Mb of DNA surrounding the jsd locus. The critical 0.4 cM jsd interval corresponds to a physical distance of approximately 1.5 Mb. Eight genes have been identified in this interval, two of which appear to be possible candidates for the jsd mutation.

Animals↗
PubMed1996

Novel amplification of non-photochemical chlorophyll fluorescence quenching following viral infection in Chlorella.

In higher plants non-photochemical dissipation of excess light, trapped by the pigment pool of photosystem II, prevents photodamage to the photosynthetic apparatus. We report here that an algal virus infecting Chlorella strain Pbi induces non-photochemical quenching of photosystem II fluorescence, indicating enhanced loss of absorbed light energy from photosystem II. This phenomenon occurs soon after the establishment of the virus infection cycle and is observed at low irradiance (20 micromol quanta m-2 s-1). At low light, infection associated non-photochemical quenching is not linked to extensive conversion of violaxanthin to antheraxanthin and zeaxanthin. However, such conversion occurs rapidly (2-10 min) in infected cells under conditions of high irradiance (100-300 micromol quanta m-2 s-1). Under similar conditions uninfected Chlorella cells do not display significant changes in non-photochemical quenching.

Carotenoids↗
PubMed1996

Do light-induced pH changes within the chloroplast drive turnip yellow mosaic virus assembly?

Turnip yellow mosaic virus (TYMV) induces gross morphological and biochemical changes in the chloroplasts of infected cells. Viral RNA is synthesized in vesicles formed by invagination of the outer chloroplast bilayer. Virion assembly occurs at the neck of these vesicles and requires illumination. Data collected over the last three decades are consistent with the hypothesis that light-induced generation of a low pH drives TYMV assembly within the intermembrane space of chloroplasts. In a low-pH environment, poly(C) regions within the genomic RNA of TYMV may interact to form tertiary structures, and the recognition of these structures by TYMV coat protein initiates virion assembly.

Chloroplasts↗
PubMed1995

Infectivity of algal viruses studied by chlorophyll fluorescence.

Algal virus infection proceeds via the specific recognition of the host cell wall, penetration of the cell wall and transfer of genetic material into the cytoplasm of the host cell. This process is similar to that which occurs when bacteriophage infect bacteria so that techniques and concepts developed to study bacteriophage are applicable to algal virus studies. By measuring virus-induced changes in chlorophyll fluorescence we have redefined classical studies on the distribution of infectivity. We show that infectivity does not follow a Poisson distribution with a fixed mean, n. By analysing the infectivity of algal viruses over a broad range of virus:cell ratios we have obtained a corrected Poisson distribution that reflects the probability of multiple virus particles attached per cell and is equally applicable to algal viruses and bacteriophage.

Chlorella↗
PubMed1995

Identification and characterization of the frog virus 3 DNA methyltransferase gene.

Cytosine DNA methyltransferases (MTases) first recognize specific nucleotide sequences and then transfer a methyl group from S-adenosylmethionine to cytosine. This division of function is reflected in five highly conserved motifs shared by cytosine MTases. The region containing the first four motifs is responsible for the catalytic function whereas the region containing the fifth motif V provides specificity of binding to DNA. In at least one case, two separate proteins, one containing the first four motifs and the second containing the last motif combine to provide full functional activity. In the frog virus 3 (FV3) genome we have identified an open reading frame (ORF) whose deduced amino acid (aa) sequence contains motifs characteristic of prokaryotic as well as eukaryotic MTases. The ORF consists of 642 bp which codes for a protein of 214 aa with a predicted molecular mass of 24.8 kDa. This ORF contains the first four highly conserved motifs of cytosine MTases but the fifth motif, responsible for DNA binding specificity, is missing. Presumably, FV3 MTase is composed of two subunits. Northern blot analysis showed that the putative MTase ORF is transcribed into two transcripts belonging to the delayed-early class of FV3 messages. These two transcripts appear to be initiated at two different start sites but terminate in the same 3' region of the gene. The transcription start sites are not preceded by any known promoter sequences, but two regions of hyphenated dyad symmetry are present at the 3' end of the message. A protein with a molecular mass of approximately 28 kDa was synthesized by a rabbit reticulocyte lysate programmed with capped runoff transcripts from the cloned gene, suggesting that the ORF can be transcribed into a message coding for a viral protein. Overall, our results suggest that we have identified a gene for a subunit of MTase in the FV3 genome.

Amino Acid Sequence↗
PubMed1994

Polycytosine regions contained in DNA hairpin loops interact via a four-stranded, parallel structure similar to the i-motif.

Thermal denaturation profiles of an oligodeoxynucleotide that forms a hairpin structure with a cytidine-rich loop show an unexpected transition at 60 degrees C at pH 5.0 but not at pH 8.0. Analytical ultracentrifugation shows that this transition reflects dimer formation via the interaction of loops from two molecules to form a novel structure termed the h-dimer. The dependence of this structure on low pH implies the formation of cytosine-protonated cytosine base pairs. NMR spectroscopy, thermal denaturation and ultraviolet absorption spectral analysis suggest a similarity to the i-motif structure recently proposed for the interaction of deoxycytidine oligomers. The use of hairpin loops to form i-motif-like structures may prove useful in searches for cognate proteins and possibly in the production of antibodies.

Base Sequence↗
PubMed1992

A frog virus 3 gene codes for a protein containing the motif characteristic of the INT family of integrases.

The integrase (INT) family of bacteriophage coded integrase-recombinase proteins are responsible for catalyzing strand exchange between DNA molecules and play an important role in the DNA replication of many bacteriophages. Within the frog virus 3 (FV3) genome we have identified an open reading frame (ORF) of which the deduced amino acid sequence contains a motif characteristic of the INT family of integrases-recombinases. The ORF consists of 825 bp which codes for a protein of 275 amino acids with a predicted Mr of 29,945. RNA transcribed from this ORF during virus infection was detected by Northern blot analysis and it is a delayed early message of approximately 1100 bases. The 5' and 3' ends of the putative FV3 integrase-recombinase transcript were mapped. The transcriptional start site is preceded by a presumptive TATA box, and a region of hyphenated dyad symmetry is present at the 3' end of the message. A protein with an Mr of approximately 30,500 was synthesized by a rabbit reticulocyte lysate programmed with capped runoff transcripts from the cloned gene, indicating that the ORF can be transcribed into a message coding for a viral protein. In the FV3 life cycle, DNA replication occurs in a large complex formed through the recombination of small viral DNA molecules. Thus, at this stage, DNA replication and recombination are interlinked. Resolution of concatameric DNA is required for the packaging of genomes into virus particles. The putative FV3 INT gene may be involved in one or more of these functions.

Amino Acid Sequence↗
PubMed1991

The termini of the chlorella virus PBCV-1 genome are identical 2.2-kbp inverted repeats.

The Chlorella virus PBCV-1 genome is a linear nonpermuted 333-kbp dsDNA molecule with covalently closed hairpin termini. The termini (minus the hairpin) are identical inverted repeats of at least 2185 bases after which the sequence diverges. The inverted repeats contain two small potential open reading frames and several direct repeats. However, neither the open reading frames nor the remainder of the inverted repeats are transcribed during PBCV-1 replication. Twenty-nine other Chlorella virus DNAs, of 36 tested, hybridized to the PBCV-1 terminal fragments.

Amino Acid Sequence↗
PubMed1989

Chlorella viruses contain linear nonpermuted double-stranded DNA genomes with covalently closed hairpin ends.

Pulsed field electrophoresis established that Chlorella viruses contain linear, nonpermuted, 330- to 380-kb dsDNA genomes. Terminal DNA restriction fragments of one virus, PBCV-1, were identified by Bal31 exonuclease digestion; the termini probably contain covalently closed hairpin ends. The end fragments cross-hybridize indicating terminal repetition; the region of repetition extends no more than 2.5 kb from the ends.

Chlorella↗
PubMed1989

Characterization of DNA polymerases in an uninfected and virus PBCV-1-infected green alga--Chlorella strain NC64A.

Chlorella NC64A cells infected with the large double-stranded DNA-containing virus PBCV-1 and uninfected cells were assayed for DNA polymerase activity. Both uninfected and infected cells contained three forms of DNA polymerase activity: (i) an exogenous DNA-dependent 10,000 g soluble fraction, (ii) an exogenous DNA-dependent 10,000 g particulate fraction, and (iii) a DNA-independent 10,000 g particulate fraction. The three DNA polymerase activities in the infected and uninfected cells were distinguished from one another by the conditions required for optimum activity and by their sensitivity to inhibitors.

Chlorella↗
PubMed1981

Detection and identification of FIJI disease virus in infected sugarcane by immunodiffusion, immuno-osmophoretic and enzyme-linked immunosorbent assays.

Radial double-immunodiffusion, immuno-osmophoretic and enzyme-linked immunosorbent assay (ELISA) methods have been compared for the detection of Fiji disease virus (FDV) in infected sugarcane tissue extracts using an antiserum containing antibodies specific to FDV proteins and ds-RNA. ELISA was the most sensitive of these tests and detected only FDV-specific proteins byt not ds-RNA. Immuno-osmophoretic tests were less sensitive than ELISA but detected both the protein and ds-RNA antigens as distinct precipitin lines. Immunodiffusion tests were much less sensitive for the detection of FDV antigens than either ELISA or immuno-osmophoretic tests. FDV antigens were detected in leaves of virus-infected sugarcane, but only in tissues of the galls which develop in response to infection. Even ELISA failed to detect any antigens in normal tissues adjacent to galls. It is concluded that for the identification to FDV in infected surgarcane, it is necessary to observe galls which can then be tested for the presence of FDV antigens. Immuno-osmophoresis appears to be a satisfactory method for such tests.

Antigens, Viral↗