A major, late 6-kilobase (6-kb) mRNA mapping in the large unique region of herpes simplex virus type 1 (HSV-1) was characterized by using two recombinant DNA clones, one containing EcoRI fragment G (0.190 to 0.30 map units) in X.

Recombinant bacteriophage lambda clones from a cat genomic library derived from placental DNA of a specific pathogen-free cat were screened to identify endogenous feline leukemia virus (FeLV) sequences. Restriction endonuclease mapping of four different clones indicates that there are a number of similarities among them, notably the presence of a 6.0- to 6.4-kilobase pair (kbp) EcoRI hybridizing fragment containing portions of sequences homologous to the gag, pol, env, and long terminal repeat-like elements of the infectious FeLV. The endogenous FeLV sequences isolated are approximately 4 kbp in length and are significantly shorter than the cloned infectious FeLV isolates, which are 8.5 to 8.7 kbp in length. The endogenous elements have 3.3- to 3.6-kbp deletions in the gag-pol region and approximately 0.7- to 1.0-kbp deletions in the env region. These deletions would render them incapable of encoding an infectious virus and may therefore be related to the non-inducibility of FeLV from uninfected cat cells and the subgenomic expression of these endogenous sequences in placental tissue. It appears that there is conservation in the ordering of restriction sites previously reported in the proviruses of the infectious FeLVs in sequences corresponding to the pol and env boundary as well as the region spanning the env gene of the endogenous clones, whereas a greater divergence occurs among restriction sites mapped to the gag and part of the pol regions of the infectious FeLV. Such deleted, FeLV-related subsets of DNA sequences could have originated either by germ-line integration of a complete ecotropic virus followed by deletion, or by integration of a preexisting, defective, deleted variant of the infectious virus.

Total cellular polyadenylated RNA from a variety of fresh human lymphoma and leukemia cells, characterized by histopathology and certain cell surface markers, was analyzed for the expression of three distinct cellular oncogenes (c-onc genes), c-erbB, c-myc and c-myb by dot-blot hybridization assays. Probes used were molecularly cloned DNA containing the respective oncogene sequence of avian erythroblastosis virus, myelocytomatosis virus (MC29) and myeloblastosis virus. All lymphoma-leukemia cells irrespective of B, T or non-B/non-T lymphocyte lineage expressed the c-erbB locus. This gene was also found to be active in normal peripheral blood lymphocytes and lymphocytes from lymph nodes showing reactive hyperplasia. This observation suggested that c-erbB might be normally involved in cell growth functions since it was not unique to hematopoietic malignancies. In contrast to c-erbB, elevated expressions of c-myc or c-myb were detected in certain neoplasms of B-lymphocytes and some other lymphoproliferative disorders as compared to the majority of the samples tested which showed either low or undetectable levels of these transcripts. An examination of B-cell lymphomas and leukemias in which the majority of the cellular populations expressed either Kappa or lambda surface lg light chain molecules revealed variations in the levels of c-onc transcripts within a morphologic and immunologic subtype. These findings support the notion that, in general, genetic heterogeneity exists in groups of hematopoietic proliferations defined by conventional histopathologic and immunologic criteria. Although with the majority of the specimens there was no obvious correlation between the morphologic cell type of lymphoma/leukemia and the c-onc RNA levels, interestingly two of the three samples diagnosed as chronic lymphocytic leukemia, B-cell type, showed considerably increased transcription of the c-myc gene relative to the other B-cell neoplasms. Thus a class of differentiated B-cell leukemia has been identified in which the molecular mechanisms which affect c-myc gene expression can now be investigated.

No abstract