Ty elements transpose through an RNA intermediate

Retroviruses have proved to be useful reagents for studying genetic and epigenetic (such as regulatory) changes in eukaryotic cells, for assessing functional and structural relationships between transposable genetic elements, for inducing insertional mutations, including some important in oncogenesis, and for transporting genes into eukaryotic cells, either after natural transduction of putative cellular oncogenes or after experimental construction of recombinant viruses. Many of these properties of retroviruses depend on their capacity to establish a DNA (proviral) form of their RNA genomes as a stable component of host chromosomes, in either somatic or germinal cells.

http://science.sciencemag.org/content/sci/216/4548/812.full.pdf

Form and function of retroviral proviruses

Analysis of FBJ-MuSV provirus and c-fos (mouse) gene reveals that viral and cellular fos gene products have different carboxy termini

We wished to construct cell lines that supply the gene products of gag, pol, and env for the growth of replication-defective reticuloendotheliosis retrovirus vectors without production of the helper virus. To do this, first we located by S1 mapping the donor and acceptor splice sites of reticuloendotheliosis virus strain A. The donor splice site is ca. 850 base pairs from the 5' end of proviral DNA. It is close to or overlaps the encapsidation sequences for viral RNA. The splice acceptor site is ca. 5.6 kilobase pairs from the 5' end of proviral DNA. Therefore, the encapsidation sequences and the donor splice site were removed from viral DNA to give expression of the gag and pol genes without virus production. The promoter in the long terminal repeat was fused to a site near the first ATG codon of the env gene, thereby deleting the encapsidation sequences and the gag and pol genes to give expression of the env gene without virus production. The permissive canine cell line D17 was transfected with the two modified viral DNAs. Two cell clones that contain both modified viral DNAs support the production of replication-defective spleen necrosis virus-thymidine kinase recombinant retrovirus vectors without the production of helper virus. To prevent recombination, the vector contains deletions that overlap with deletions in the integrated helper virus DNAs. This helper cell-vector system will be useful to derive infectious recombinant virus stocks of high titer (over 10(5) thymidine kinase transforming units per ml) which are able to infect avian, rat, and dog cells without the aid of helper virus.

Construction of a helper cell line for avian reticuloendotheliosis virus cloning vectors

Five peptides containing amino acid sequences from the type 1 poliovirus structural protein VP1 have been synthesized. Each of the peptides was found capable of priming the immune system of rabbits for a long-lasting, virus-neutralizing IgG antibody response following a single inoculation of intact virus. One peptide directly induced the production of neutralizing antibody.

Priming for and induction of anti-poliovirus neutralizing antibodies by synthetic peptides

Antibodies were raised in rats against the poliovirus type 1 capsid proteins, VP1, VP2, and VP3. Antibodies directed against VP1 from type 1 poliovirus (Mahoney) neutralized type 1 but not type 2 poliovirus. Antibodies raised against VP2 and VP3 failed to neutralize type 1 virus. Thus, VP1 appears to be a neutralizing antigen for poliovirus and in its denatured form presents to the immune system its neutralizing determinants.

https://www.pnas.org/content/pnas/79/23/7518.full.pdf

Marie Chow

Papers

Isolated poliovirus capsid protein VP1 induces a neutralizing response in rats

Synthesis of murine leukemia virus plus strong stop DNA initiates at a unique site.