Downregulation of Waf1, C2, C3, and major histocompatibility complex class I loci within an 18-cM region of chromosome 17 in adenovirus-transformed mouse cells.

In this study, the expression of the p53 tumor suppressor gene and the p53-regulated Mdm2 and Waf1 genes was evaluated in adenovirus (Ad)-transformed mouse cells. The expected levels of p53 mRNA and protein and Mdm2 mRNA were detected in all transformed cells. However, the level of Waf1 mRNA was markedly reduced in Ad12-transformed cells and in some Ad5-transformed cells. Waf1 expression was not reduced in untransformed mouse cells infected with Ad12 or Ad5. Expression of the class I major histocompatibility complex (MHC) locus was downregulated in 13 Ad-transformed cell lines (derived from four different strains of mice) that exhibited reduced expression of Waf1. Waf1 is located on mouse chromosome 17 proximal to the MHC class I locus. To determine whether other chromosome 17 genes were downregulated, the cells were examined for expression of other genetic loci. Of those tested, only the C2 and C3 complement loci were expressed in mouse fibroblasts. Expression of C2 (which is within the MHC) and expression of C3 (which is 15 cM distal to the MHC) were downregulated in those transformed cells in which Waf1 and MHC class I were downregulated. The Ad12- and Ad5-transformed cells that expressed low levels of Waf1, MHC class I, C2, and C3 formed tumors in syngeneic adult mice. These data suggest that the downregulation of multiple genes within the 32 Mb of mouse chromosome 17 that includes the Waf1 locus to the C3 locus occurs in Ad mouse-cell transformation and may contribute to the tumorigenicity of transformed cells.

A p53 mutation in exon 5 associated with adenovirus transformation.

The adenovirus type 5 (Ad5) 55-kDa E1B oncoprotein has been shown to form complexes with the p53 tumor suppressor protein. These complexes are thought to interfere with normal p53 activity and may be responsible for the paucity of p53 mutations in cells transformed by these viruses. This report describes an example of a p53 mutation in exon 5 in an Ad5-transformed cell line that exhibited less expression of E1B 55-kDa protein and a longer tumor-latency phenotype than another Ad5-transformed cell line expressing wild-type p53. The finding of a p53 mutation in an Ad5-transformed cell line is unusual, especially considering the current theory that p53-E1B interactions play an important role in adenovirus transformation. This mutation could represent an alternative method of inactivating p53 function in the absence of sufficient levels of E1B 55-kDa oncoprotein.

Three distinct H-2Ks molecules differing at the carboxy terminus are expressed on a tumor from SJL/J mice.

A dimethylbenzanthracene-induced leukemia of H-2s origin expressed at least two class I molecules on the cell surface that were precipitated by anti-H-2.19, an alloantiserum prepared against the private H-2Ks specificity. Mapping studies in recombinant inbred strains along with comparisons of tryptic peptide maps and N-terminal sequences indicated that the proteins were virtually identical and probably encoded by the same class I gene. When cells were labeled in the presence of tunicamycin, the proteins precipitated by anti-H-2.19 were further resolved into three distinct peptides. Experiments were performed to determine which of these various proteins were phosphorylated and which were recognized by an anti-synthetic peptide serum directed against the ultimate C-terminus of H-2K class I molecules. The results indicate that a single class I gene from the H-2Ks region may encode three class I molecules that differ only at the C-terminus due to alternative splicing of pre-mRNA.

A novel H-2s class I molecule expressed on a B-cell leukemia from SJL/J mice.

Anti-H-2.33 [(B10.D2 X A)F1 anti-B10.A(5R)], which predominantly contains antibodies recognizing H-2Kb and IAb molecules, was found to be cytotoxic against DMLM 1678, a B-cell leukemia of SJL/J (H-2s) origin. The antiserum precipitated a typical class I (H-2-like) molecule from labeled tumor cell preparations as judged by molecular mass, papain susceptibility and association with beta 2-microglobulin. Sequential immunoprecipitation studies revealed that it was distinct from either H-2Ks or H-2Ds, the 2 molecules expressing the private antigens of the H-2s haplotype. Absorption analysis using congenic mice mapped the gene controlling the expression of the novel molecule telomeric to the S-region within the major histocompatibility complex.

Occurrence of a unique MHC class I gene in distantly related members of the genus Mus.

There is unequivocal evidence that a relatively nonpolymorphic class I gene (designated Q10) from the Qa region of inbred mice encodes a secreted class I molecule. We have used a cDNA probe specific for this gene and an antiserum specific for its secreted protein product to investigate the occurrence and expression of this gene in different species of wild mice broadly representing the entire genus Mus. Evidence is presented that a Q10-like gene has been conserved and is transcribed and translated throughout the genus, suggesting that it serves an important function. However, the data also show that some differences have appeared in this gene over the period of evolutionary time covered by this sampling of wild mice. These results indicate that a specific class I DNA probe isolated from inbred mice can be used to discriminate a particular gene among the multiple class I genes present in other species.

Purification of a glycoprotein bearing a tumor transplantation antigen specific for Friend, Moloney, and Rauscher MuLV-induced tumors.

A 175,000 dalton glycoprotein bearing a tumor-associated transplantation antigen (TATA) has been isolated from a Rauscher-MuLV-induced leukemia (RBL-5). The glycoprotein has the properties expected for a Friend, Moloney, or Rauscher-MuLV-induced TATA: 1) It is synthesized by RBL-5 cells and is expressed on the cell surface. 2) When inoculated into mice, it provides complete protection against challenge with RBL-5 cells at doses of 1 microgram or less. 3) The same protein, isolated from a Moloney-MuLV-induced leukemia, also protects mice against challenge with RBL-5. A similar glycoprotein is expressed on other tumor cells and on normal cells that do not express a TATA cross-reactive with RBL-5. Therefore, the immunogenicity of this molecule cannot be principally accounted for by either its unique or elevated expression on RBL-5 cells. A model is presented that accounts for these properties of the RBL-5 TATA. In addition, two other features of the RBL-5 TATA are discussed; an apparent abrogation of immunity seen only with certain doses of antigen, and a loss of the inherent immunogenicity of gp175 during purification.

Definition of two LD antigens in rhesus monkeys.

Two rhesus (Macaca mulatta) monkey lymphocyte-defined (LD) antigens have been identified using two typing cells as stiumlators in a one-way mixed leukocyte culture (MLC) assay. An analysis of the genetic behavior of these LD antigens in six rhesus monkey families revealed that both antigens were linked with RhLA. One probable recombinant indicated that the LD locus lies outside the two known RhLA-SD loci and the locus which controls the serum protein, properdin B(Bf). These two antigens, LD1 and LD2, had observed gene frequencies of 0.07 and 0.25, respectively. Neither of these two new LD antigens was significantly associated with any serologically defined (SD) antigen.

Conditions for generating and assaying human leukocyte inhibitory factor (LIF) induced by purified protein derivative (PPD).

This report examines a variety of experimental conditions for the production of human leukocyte inhibitory factor (LIF). The data indicate that the production of LIF as measured in the indirect capillary-tube migration inhibition assay using human polymorphonuclear indicator cells accurately reflects delayed hypersensitivity to purified protein derivative (PPD) as detected by skin-test reactivity. Mononuclear cells and semipurified lymphocytes separated from whole blood by sedimentation in Ficoll-Hypaque were able to generate LIF in response to PPD. The quantity of cells responsible for LIF production were standardized and as little as 1 x 10(6) mononuclear cells were required for detectable LIF production. LIF produced by mononuclear cells required only temporary exposure to PPD, thus eliminating the necessity for a control to which antigen was added at the end of culture to antigen-free supernatants. In addition, the removal of antigen after a brief exposure helps to avoid the possible toxic effect of some antigens on the migrating polymorphonuclear leukocytes (PMNL) population. LIF production did not require extraneous serum protein (i.e., fetal bovine serum). Further, kinetic studies indicated that LIF was detected as early as 8 hr following a 2 hr-exposure to PPD and that even a 1 hr-exposure was sufficient to generate measurable detectable quantities of LIF. After 48 hr of culture, supernatants were found to contain considerable amounts of LIF, with reactivity at dilutions as high as 1:40.