Is the anti-sarcoma and anti-viral cytokine "plasma factor" a novel chicken Y-box protein?

A line of research beginning in the early 1960s with the observation that West Nile virus and, later, several strains of rabies virus could inhibit the development of the Rous sarcoma virus-induced tumor in the wing-web of chicken (a "sarcoma-blockade") eventually culminated in the characterization of a 14-kDa circulating anti-sarcoma and anti-viral activity christened "plasma factor" (PF) which, unlike the interferons, inhibited the replication of diverse RNA-containing viruses, but not of any DNA-containing viruses. The possibility that this 14 kDa protein represented a novel antiviral cytokine has been strengthened by analysis of partial amino acid sequencing data which suggest that this 14-kDa cytokine may correspond to the 127-amino acid-long chicken YB2-like protein (Locus: XP_423576) deduced very recently from the genomic sequencing of chicken. Biologically, proteins of the Y-box family (such as chicken YB1 and YB2) not only bind DNA and thus regulate transcription but also bind single-stranded RNA in a sequence-specific and reversible manner, repress viral RNA translation, inhibit retroviral transformation of chicken fibroblasts, and are known to regulate transcription of human immunodeficiency virus and hepatitis B virus. Taken together, the available data point to a novel anti-viral cytokine with a novel mechanism of action.

Expression of Rous Sarcoma Virus Enhancer Factor Gene in Human Hepatocellular Carcinoma / 대한암학회지

PURPOSE: We have previously cloned three enhancer factor genes encoding proteins that bind to long terminal repeats (LTRs) of Rous sarcoma virus. Among these genes, RSV- EF-I gene is expressed in rat hepatoma tissues and several proliferating cell lines but not in normal rat liver tissues. We have isolated the human homologue of RSV-EF-I gene and examined its expression in human hepatocellular carcinoma tissues. MATERIALS AND METHODS: We have screened the human genomic library and cDNA library of Hep G2 cell line derived from human hepatocellular carcinoma to isolate the human homologue of RSV-EF-I gene. RESULTS: We have isolated one cDNA clone containing about 1.5 kb insert and sequenced. Sequence analysis reveals that this human homologue of RSV-EF-I gene has a high similarities to human YB-1 mRNA, human DNA-binding protein B (dbpB) gene and other Y-box protein genes. It is expressed in human hepatocellular carcinoma but very slightly in normal human liver tissues in Northern blot analysis. CONCLUSION: Our data suggest that the human homologue of RSV-EF-I gene presumably belongs to Y-box protein family genes and plays a role in the transformation of the human hepatoma cells.

Genetics of post-hatching survival potential of Australorp chicks infected as embryos by subgroup A Rous sarcoma virus: further support to 4-allele genetic model.

Embryos (II day-old) of Australorp breed were inoculated via chorioallantoic membrane (CAM) with subgroup A Rous sarcoma virus, and hatched subsequently. The post-hatch survival period in chicks was recorded upto the last chick that died by virus-induced liver tumour, which had a range from 3 to 50 days with an average of 13 +/- 8.7 days. The survival potential of progency tested Australorp parents selected on the basis of negative CAM-infection and those selected on uninoculated embryos, differed significantly (P less than 0.01) while maintaining an inverse relationship between liver tumour mortality and degrees of infection of CAMs. The homozygous susceptibles lacking either ar1 or ar2 or both alleles of the tva (tumour virus a) locus died within 7 days of post-hatching, supporting thereby 4-allele genetic model of tva locus recently proposed for the control of LT- and CAM-infection phenotypes.

Induced liver tumour deaths by subgroup A Rous sarcoma virus in chicks inoculated via chorioallantoic membrane, a genetic marker.

A study was made using two strains of light breed (White Leghorn strains, A and B) and four heavy beeds (Rhode Island Red, New Hampshire, Australorp, Columbian) to evaluate the breed difference in survival potential of chicks that were infected as 11-day-old embryos via chorioallantoic membranes (CAMs) with a subgroup A Rous sarcoma virus. Of the 1185 chicks hatched over multiple hatch-replicates, 845 chicks died rapidly of a fibrosarcomatous liver tumour (LT) with a peak mortality about 74% attained by the second week, post-hatch, in the heavy breeds and more than 90% by the second week in the light breed. The breeds did not differ in induced LT mortality when the chicks hatched from eggs that had at least 25 pock counts on CAMs, apparently genetically susceptible, i.e. 25 biologically active virus particles were enough to induce an unpreventable fatal LT. However, low pock-count on CAMs did not act as a pointer for predicting genetic resistance to infection because about 23% of chicks developed from eggs that had no pocks on CAMs, apparently genetically resistant, also died of LT, requiring further studies.

Nonspecific immunoprotection against Rous sarcoma tumor in chicks.

An enzyme treated preparation of saprophytic Mycobacterium phlei, referred as NSI, when administered intramuscularly has been found to protect the chicks against Rous Sarcoma Virus induced tumor. A protection level of 35.4%, 24.1% and 21.2% were observed when challenged on 10th, 20th and 30th day post NSI inoculation. The tumor growth inhibitory-activity of NSI was significant (P less than 0.01). Both, systemic and intralesional administration of NSI exhibited significant tumorostatic activity (P less than 0.05). NSI stimulated the cell mediated immune response to specific as well as to nonspecific Rous sarcoma antigen. These studies indicated the immunopreventive activity of NSI against Rous sarcoma tumor which had an immunogenic basis.