PubMed Health⌕ Search

Biomedical subjects

J Ríman

Publications and source records attributed to J Ríman.

10 recordsLinked to original sources
PubMed1990

Binding properties of avian retroviral proteins. I. Preparation and basic characterization of ASLV NC(p12) and MA(p19).

Using SP-Sephadex column chromatography we isolated from an avian retrovirus, AMV(MAV), nucleic acid-binding proteins ASLV NC(p12) and MA(p19). As shown by several criteria, namely SDS-PAGE, PR(p15) protease activity, and nucleic acid binding assay with the use of both ss and ds DNAs, our NC(p12) and MA(p19) isolates are virtually pure proteins mutually not cross-contaminated. Rabbit anti-NC(p12) and anti-MA(p19) sera which we prepared did not cross-react mutually. We conclude that both NC(p12) and MA(p19) and antibodies against them are adequately pure preparations for investigating their nucleic acid binding specificities towards AMV(MAV) genomic RNA and MAV-1 proviral DNA using electron microscopy supported by computer analysis of electron micrographs.

Animals↗
PubMed1990

Binding properties of avian retroviral proteins. II. Binding of protein ASLV NC(p12) to viral RNA and proviral DNA.

Binding of the major avian retroviral nucleocapsid protein ASLV NC(p12) to the MAV-1 (myeloblastosis-associated virus) proviral dsDNA and viral ssRNA was analysed using electron microscopy. Specificity of the binding was estimated by special computer programs. The NC(p12) protein bound to MAV-1 proviral dsDNA (clone pAT153--MAV-1), but specificity of this binding was not found by computer evaluation. NC(p12) also bound to nondenatured 70S viral RNA at a rate of 25 +/- 3 molecules per RNA molecule. When this RNA was denatured either before or after the complexing, it showed no binding affinity for the protein. This result implies that preserved secondary structure of the viral RNA was required for the binding.

Animals↗
PubMed1990

Binding properties of avian retroviral proteins. III. Binding of protein ASLV MA(p19) to viral RNA and proviral DNA.

The binding of the avian retroviral matrix protein ASLV MA(p19) to homologous viral ssRNA and proviral dsDNA was analysed using electron microscopic methods combined with a special computer evaluation. No binding affinity of MA(p19) to homologous nondenatured or denatured viral RNA was found. In contrast, ASLV MA(p19) was shown to have one specific binding site on MAV-1 proviral dsDNA at position 6795 +/- 345 bp from the 5' end of the molecule. A second specific binding site was found in a cellular sequence.

Animals↗
PubMed1989

Transcription of the chicken myb proto-oncogene starts within a CpG island.

The nucleotide sequence of an 8.2-kb DNA fragment from the 5' proximal part of the chicken myb proto-oncogene spanning 1761 nucleotides upstream and 6436 nucleotides downstream from a presumed c-myb initiation codon was determined. A 3.3-kb G + C-rich region found in this sequence had also other features characterizing CpG islands, i.e. no CpG underrepresentation and lack of CpG methylation. In haematopoietic tissues c-myb mRNA synthesis starts in two major regions of the CpG island, namely 98 to 108 and 143 to 145 nucleotides upstream from the c-myb initiation codon. These two regions are in or close to the 124-bp evolutionarily conserved element located in the middle part of the CpG island. No alternative splicing of the 5' end of c-myb mRNA suggested earlier (1,2) was observed. The c-myb promoter contains neither TATA nor CAAT box-like structures at the usual positions. Instead, numerous potential Sp1 factor binding sites were found both upstream and downstream from the transcription initiation sites. Moreover, consensus v-myb protein DNA-binding sites were revealed in the promoter region and in sequences downstream from it.

Animals↗
PubMed1987

Monoclonal antibodies against RNA-dependent DNA polymerase from myeloblastosis-associated viruses.

Two lines of hybridomas, RT-12 and RT-14, secreting monoclonal antibodies against the reverse transcriptase from myeloblastosis-associated viruses have been prepared. The monoclonal antibodies RT-12 and RT-14 specifically react with reverse transcriptase, as has been shown by radioimmunoassay and enzyme-linked immunoassay techniques after SDS-PAGE and blotting to nitrocellulose membranes. It has been shown that antigenic determinants for RT-12 and RT-14 are stable to SDS denaturation, hence they belong to a linear type; they are located on the alpha subunit of the enzyme.

Animals↗
PubMed1976

Stepwise dissociation of high molecular weight avian myeloblastosis virus RNA: 30-40S RNA subunits--the best natural template-primer for viral reverse transcriptase.

Controlled disruption of 60S AMV RNA with formamide was used to prepare 50-55S and 30-40S RNAS. When the activities of these RNAs as templates for AMV reverse transcriptase were compared it was found that 50-55S RNA was 1-5 times and 30-40S RNA 2 to 3 times more active than 60S RNA. The 30-40S RNA produced by heating, instead of formamide disruption, was inactive as a template but activity was restored by addition of oligo(dT). 40% of the 4S RNA initially associated with the 60S RNA remained associated with all the RNA species obtained by formamide treatment but was lost on heating. It is concluded that this RNA acts as resident primer whereas the other 60% of the 4S RNA is less firmly bound and appears to have little or no primer activity. Removal of the less firmly bound 4S RNA increases the template activity of the viral RNA.

Avian Leukosis Virus↗
PubMed1976

The oncornavirus maturation process: quantitative correlation between morphological changes and conversion of genomic virion RNA.

Avian myeloblastosis virus (AMV) was harvested at different time intervals from chick leukemic myeloblasts, and the rate of the maturation process of AMV was estimated on the basis of morphological changes in the virions and conversion of genomic viral RNA. The change from immature virions characterized by the presence of an electronlucent center to the condensed mature form (with dense nucleoid) was accompanied by the conversion of 30-40S RNA to 60S RNA. Both processes were quantitatively defined, correlated, and found to proceed in parallel at the same speed. Early stages of maturation were characterized by a high turnover of immature to mature virions; 31-40% of the mature forms were found in 3.5-min virus harvests. The rate of this process decreased with time. The 17-hour harvests still revealed the presence of 10-15% of immature virions. The course of the maturation process is discussed.

Animals↗
PubMed1976

Stepwise transition of aggregate structure of high-molecular-weight avian myeloblastosis virus RNA. Mode of releasing of associated 4S RNA.

Mode of releasing of associated 4S RNA species was studied during a controlled transition of aggregate structure of high-molecular-weight AMV-RNA. It has been found that associated 4S RNA constitutes 2.5% of 60S AMV-RNA complex. Approximately 60% of associated 4S RNA is successively released during treatment of viral RNA with increasing formamide concentration, concomitantly with the transition of 60S RNA aggregate through 50--55S RNA intermediate into the final 30--40S RNA subunits. 40% of 4S RNA remains associated with 30--40S RNA subunits prepared by formamide treatment and can be released from them by heating. A procedure is thus provided both for the isolation of oncornaviral RNA subunit structures deprived of various partions of associated 4S RNA and for the fractionation of 4S RNA species according to their binding affinity to the genome oncornaviral RNA.

Avian Leukosis Virus↗
PubMed1975

Polypeptides isolated from ribosome-like structures occluded in avian myeloblastosis virus (AMV).

The protein composititon of ribosome-like particles isolated from AMV was determined by acrylamide gel electrophoresis and by immunological methods. It was established that the protein spectrum of ribosome-like particles differed significantly form the total protein spectrum of AMV. The most characteristic protein components of ribosome-like particles had a molecular weight in the range of 70 000--110 000. Apart from these proteins, the viral ribosomal particles contained a small amount of proteins with a molecular weight of 14 000--35 000 that could not be removed even by extensive purification. Immunological studies of the proteins of ribosome-like particles revealed the presence of antigenic determinants of ribosomal proteins. Furthermore, throughout the purification procedure the material contained components that reacted with antibodies against gs antigens.

Animals↗