Properties of feline leukemia virus. III. Analysis of the RNA.

The kinetics of virus labeling was used to study the maturation of viral RNA in the Rickard strain of feline leukemia virus. Viral RNA labeled over differing intervals was characterized by gel electrophoresis and velocity sedimentation in sucrose gradients made up in aqueous buffer and 99% dimethyl sulfoxide. Labeled virus was found within 30 min after adding radioactive uridine to the cells and production of labeled virus reached a maximum at 4 to 5 h after pulse labeling. Native RNA from feline leukemia virus resolved into three size classes when analyzed by electrophoresis on 2.0% polyacrylamide-0.5% agarose gels: a 6.2 x 10(6) to 7.1 x 10(6) mol wt (50 to 60S) class, an 8.7 x 10(4) mol wt (approximately 8S) class, and a 2.5 x 10(4) mol wt (4 to 5S) class. From two experiments during which RNA degradation appeared minimal, these made up to 57 to 76%, 2 to 5%, and 6 to 12%, respectively, of the total RNA. The 8S RNA in feline leukemia virus has not previously been reported. The 50 to 60S RNA from virus harvested after 4 h of labeling electrophoretically migrated faster and sedimented more slowly in sucrose gradients than did the same RNA species harvested after 20 h of labeling. This argues for an intravirion modification of the high-molecular-weight RNA. The large subunits of denatured viral RNA from both 4- and 20-h labeled-viral RNA electrophoretically migrated with an estimated molecular weight of 3.2 x 10(6) but sedimented with 28S ribosomal RNA (1.8 X 10(6) mol wt) when analyzed by velocity sedimentation through 99% dimethyl sulfoxide.     

Structure of the Abelson murine leukemia virus genome.

Virions produced from cells transformed by A-MuLV contain a 30S, 5.6 kb RNA that can be translated in a cell-free system to form the characteristic A-MuLV protein. This RNA was mapped by heteroduplex methods using DNA probes from M-MuLV, the presumed parent of A-MuLV. The overall organization of the RNA was determined by using full-length M-MuLV reverse transcribed DNA and visualizing the heteroduplexes in the electron microscope. This showed that A-MuLV and M-MuLV have homologous sequences at both ends of their RNAs but that the central portion of the A-MuLV genome is not homologous to sequences in M-MuLV RNA. A precise measure of the lengths of the shared regions was obtained by using S1 nuclease to digest hybrids between 32P-labeled M-MuLV DNA and A-MuLV RNA; the resulting fragments were analyzed for their length by electrophoresis. The regions of homology were shown to be 1320 nucleotides long at the 5' end and 730 nucleotides long at the 3' end. Thus approximately 6200 nucleotides of the approximately 8300 in M-MuLV RNA were deleted when the A-MuLV genome was formed, but an insert of 3600 nucleotides, presumably derived from the normal murine genome, was inserted in place of the deleted region.     

Relationship of retroviruses isolated from human leukemia tissues to the woolly monkey-gibbon ape leukemia viruses.

Retroviruses have been isolated from the tissues of human leukemia patients. Previous studies have shown that these isolates share some antigenic determinants with the family of viruses isolated from the woolly monkey and gibbon ape and that they exhibit partial nuclei acid homology with this same group of viruses. We have compared the RNAs of the viruses by two-dimensional polyacrylamide gel electrophoresis of the large RNase T1-resistant oligonucleotides. The degree of sequence identity between the RNAs was determined by the similarity of their RNase T1-resistant oligonucleotide pattern on gels, fingerprints, and in some cases by partial sequence analysis of individual oligonucleotides. This technique permits us to determine the degree of sequence identity among related RNA species. From our studies we conclude that viruses isolated from the tissues of two human leukemia patients, A1476 and SKA 21-3, as well as some subcultures of a virus isolated from the leukemic tissues of a third patient, HL23V, are closely related to the wooly monkey virus. However, the fingerprints of other HL23 viral isolates are very similar to that of GaLVSF, a gibbon ape leukemia virus isolated from a lymphosarcoma.     

Problems in the genetics of bovine leukemia. II. The effect of fathers and mothers on the leukemia disease frequency in the progeny

Geneology of 14,000 animals which are the progeny of 554 bulls are studied, 2060 of them having leucosis. Differences between bulls in the frequency of the disease in daughters are observed. The morbidity of daughters of bulls having leucosis is higher than for the population in the average. The morbidity of the animals depends on the linear relation animals. "Leucosis" families having a high concentration of ill animals for several generations, and families resistant to leucosis are revealed. Daughters of leucosis mothers got ill more often than those of healthy animals. The coefficient of heritability of leucosis ranges from 0.07 to 0.50. Concordancy for leucosis in unisexual twins is 74.1%. Insignificant increase in leucosis is found for the last three generations. Predisposition for leucosis is characterized by a complex hereditary condition. The portion of genetic factors is quite enought to conduct the animal selection for leucosis resistance.     

Anticipation in familial leukemia.

Anticipation refers to worsening severity or earlier age at onset with each generation for an inherited disease and primarily has been described for neurodegenerative illnesses resulting from expansion of trinucleotide repeats. We have tested for evidence of anticipation in familial leukemia. Of 49 affected individuals in nine families transmitting autosomal dominant acute myelogenous leukemia (AML), the mean age at onset is 57 years in the grandparental generation, 32 years in the parental generation, and 13 years in the youngest generation (P < .001). Of 21 parent-child pairs with AML, 19 show younger ages at onset in the child and demonstrate a mean decline in age at onset of 28 years (P < .001). Of 18 affected individuals from seven pedigrees with autosomal dominant chronic lymphocytic leukemia (CLL), the mean age at onset in the parental generation is 66 years versus 51 years in the youngest generation (P = .008). Of nine parent-child pairs with CLL, eight show younger ages at onset in the child and reveal a mean decline in age at onset of 21 years (P = .001). Inspection of rare pedigrees transmitting acute lymphocytic leukemia, chronic myelogenous leukemia, multiple types of leukemia, and lymphoma is also compatible with anticipation. Sampling bias is unlikely to explain these findings. This suggests that dynamic mutation of unstable DNA sequence repeats could be a common mechanism of inherited hematopoietic malignancy with implications for the role of somatic mutation in the more frequent sporadic cases. We speculate on three possible candidate genes for familial leukemia with anticipation: a locus on 21q22.1-22.2, CBL2 on 11q23.3, and CBFB or a nearby gene on 16q22.