Mammary tumor induction loci in GR and DBAf mice contain one provirus of the mouse mammary tumor virus

Michalides, Rob; Nie, R. Van; Nusse, Roeland; Hynes, Nancy E.; Groner, Bernd

doi:10.1016/0092-8674(81)90281-6

Cited by 97 publications

(64 citation statements)

References 25 publications

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“…It has been shown that the Mtv-2 locus contains two EcoRI fragments of 10.5 and 6.6 kb (21,22); thus, clone GR-40 does not contain the provirus associated with the Mtv-2 locus but another of the endogenous proviruses.…”

Section: Resultsmentioning

confidence: 99%

Hormone-responsive expression of an endogenous proviral gene of mouse mammary tumor virus after molecular cloning and gene transfer into cultured cells.

Hynes¹,

Kennedy²,

Rahmsdorf³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

155

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A recombinant A phage containing mouse mammary tumor virus (MMTV) proviral DNA was isolated from a gene library constructed from GR mouse liver DNA. Restriction enzyme analyses reveal that the cloned molecule contains a copy of one ofthe GR endogenous MMTV proviruses flanked on both sides by 2-3 kb ofmouse genomic DNA. In this report we have examined the expression of the cloned MMTV provirus after cotransfection with the herpes thymidine kinase (TK; ATP:thymidine 5'-phosphotransferase, EC 2.7. The regulation of mouse mammary tumor virus (MMTV) expression provides an excellent experimental system for the study of steroid hormone action. In cultured cells, the levels of MMTV RNA and virus can be stimulated by glucocorticoid hormones acting through a cytoplasmic hormone receptor protein (1-3). This stimulation ofviral RNA synthesis is very rapid, being independent of simultaneous protein synthesis (3,4) and apparently caused by an increase in the rate of transcription of MMTV proviral DNA (5, 6). Therefore, it appears that glucocorticoids exert their effect upon MMTV directly at the level of viral RNA transcription.A more detailed analysis of the hormonal regulation of MMTV transcription can be carried out upon purification ofthe molecular components involved. By using molecular cloning techniques, we have isolated a A phage-mouse DNA recombinant molecule that contains an MMTV provirus flanked by 2-3 kilobase (kb) ofgenomic DNA. This recombinant molecule was isolated from a gene library constructed from liver DNA taken from GR mice. This mouse strain is known to have 5 MMTV endogenous proviruses (7). To study expression of this MMTV provirus we have introduced the gene into cultured cells by using a DNA-mediated transformation technique. We show that after cotransfection of this A phage-MMTV-containing recombinant DNA with the herpes thymidine kinase (TK; ATP:thymidine 5' phosphotransferase, EC 2.7.1.21) gene into mouse LTK-cells (8), a high percentage of the TK+ transformants contain the MMTV proviral DNA. In at least one of the LTK+ cell clones, the cotransfected MMTV provirus is transcribed to yield MMTV RNA, which appears identical in size to that present in virus-producing cells. Finally, we have observed that in the presence of dexamethasone, these LTK+ MMTV-transfected cells have increased levels of MMTV RNA. We interpret these results as follows. Because the regulatory property (i.e., the hormone-responsive increase in the concentration of MMTV RNA) is cotransferred with the cloned DNA containing the MMTV provirus, the primary DNA sequence responsible for the mediation of the hormone effect is probably located within the sequence of the cloned DNA. MATERIALS AND METHODS Isolation and Restriction EnzymeMapping of A Phage-MMTV Recombinant DNA. DNA isolated from liver tissue of GR mice (7) was partially digested with EcoRI to yield average size of 20 kb and was preparatively fractionated on an agarose gel. The DNA (14-24 kb) was recovered and 3 ,ug was ligated with 2 ,ug of A Charon 4A arms and packa...

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Section: Resultsmentioning

confidence: 99%

Hormone-responsive expression of an endogenous proviral gene of mouse mammary tumor virus after molecular cloning and gene transfer into cultured cells.

Hynes¹,

Kennedy²,

Rahmsdorf³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

155

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“…Each high incidence mouse strain congenitally transmits highly infectious MMTV through the milk to their o spring. In addition, the C3H (Michalides et al, 1981, Smith and Vlahakis, 1982, van Nie and Verstraeten, 1975, Vlahakis et al, 1970 and GR (Michalides et al, 1985, van Nie et al, 1977 mouse strains each contain a dominantly-expressed, genetically transmitted or endogenous MMTV proviral genome (Mtv-1 and Mtv-2, respectively) that encodes an infectious virus that is also present in the milk. Parous C3H females develop pregnancy independent mammary tumors that frequently arise as clonal outgrowths from preneoplastic hyperplastic alveolar nodules (HAN) at 7 ± 10 months of age (Squartini, 1961).…”

Section: Inbred Mouse Strains Having a High Incidence Of Mammary Tumorsmentioning

confidence: 99%

MMTV-induced mammary tumorigenesis: gene discovery, progression to malignancy and cellular pathways

2000

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The study of the mouse mammary tumor virus (MMTV) has provided important insights into the mechanisms of gene transcription regulation by steroid hormones, the mode of action of heritable super antigens and the progressive nature of neoplastic transformation in the mammary gland. Here we describe the current situation with respect to the latter aspect of MMTV biology and the prospects for further advance in our understanding of breast cancer in humans that may be expected from a continued study of MMTV-induced mammary neoplasia. MMTV is a heritable somatic mutagen whose target range is limited. Commonly, the tumorigenic capacity of MMTV is restricted to mammary gland, whereas infection is found in a variety of cell types. In order to replicate, proviral DNA must be inserted into the cell DNA and cell division is required to ®x the mutation. Yet only in the mammary epithelium does this lead to neoplastic transformation. This suggests a unique relationship between MMTV and mammary epithelium. In evaluating this relationship, we and others have discovered genes and potential gene pathways that are pertinent in mammary di erentiation and neoplasia. In addition, the clonal nature of these progressive events from normal to malignant phenotype has become increasingly clear. The weight of these observations compel us to conclude that mammary neoplasms arise from multipotent mammary epithelial cells through a process of acquired mutations that are re¯ected in the increasingly malignant nature of the population of progeny produced by these damaged stem cells.

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“…Cellular DNA (20 ,ug) was digested to completion with an excess of enzyme under the conditions recommended by the supplier. The gel electrophoresis conditions, DNA transfer, and hybridization with MMTV DNA probes were performed as described previously (22,24).…”

Section: Methodsmentioning

confidence: 99%

“…Expression of an endogenous MMTV, the MMTV provirus located in locus Mtv-2 on chromosome 18, gives rise to high levels of MMTV in the mammary gland tissue of GR mice. This virus is also transmitted to weanlings during nursing (22,31). The mouse strain GR contains five endogenous MMTV proviruses located on various chromosomes (R. Michalides et al, Virology, in press), one of which, Mtv-2, is highly expressed in mammary gland tissue of GR mice.…”

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confidence: 99%

Rearrangements in the long terminal repeat of extra mouse mammary tumor proviruses in T-cell leukemias of mouse strain GR result in a novel enhancer-like structure.

Michalides¹,

Wagenaar²,

Weijers³

1985

Mol. Cell. Biol.

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Male GR mice develop T-cell leukemia at low frequency late in life. These leukemia cells invariably contain large amounts of mouse mammary tumor virus (MMTV) RNA and MMTV proteins and have extra MMTV proviruses integrated in their DNA. We show here that the extra MMTV proviruses are all derived from the endogenous MMTV provirus associated with the Mtv-2 locus and that the T-cell leukemias are clonal with respect to the acquired MMTV proviruses. The extra MMTV proviruses in six transplantable T-cell leukemia lines studied had rearranged, shortened long terminal repeats (LTRs); each T-cell leukemia, however, had a different LTR rearrangement within its extra MMTV provirus. The alteration within the extra LTRs of T-cell leukemia line 42 involved deletion of 453 nucleotides and generation of a tandem repeat region consisting of regions flanking the deletion. This alteration generated a sequence similar to the adenovirus enhancer core sequence. The viral RNAs in the T-cell leukemias contained corresponding alterations in their U3 regions. These results demonstrate that expression of MMTV in T-cell leukemias of GR mice may be the consequence of the generation of a novel enhancer, which could also stimulate expression of any adjacent cellular oncogene.The expression, and thus the tumorigenicity, of retroviruses depends on the presence of transcriptional control elements in the long terminal repeat (LTR) of the retrovirus genome. These elements are also implicated in determining the tissue-specific expression of retroviruses (1, 2, 4, 36).The mouse mammary tumor virus (MMTV) is mainly expressed in mammary gland tissue in vivo; sporadic expression has also been observed in male reproductive organs and salivary glands (for recent reviews, see references 12 and 23). This high expression of MMTV in mammary gland tissue occurs in high-mammary-tumor mouse strains, such as RIII and C3H, due to milk transmission of and subsequent infection by an exogenous MMTV variant. Expression of an endogenous MMTV, the MMTV provirus located in locus Mtv-2 on chromosome 18, gives rise to high levels of MMTV in the mammary gland tissue of GR mice. This virus is also transmitted to weanlings during nursing (22, 31). The mouse strain GR contains five endogenous MMTV proviruses located on various chromosomes (R. Michalides et al., Virology, in press), one of which, Mtv-2, is highly expressed in mammary gland tissue of GR mice. A high level of expression, however, is observed in T-cell leukemias that develop infrequently in male GR mice after a long latency period (11). These T-cell leukemias contain incompletely processed precursor proteins of MMTV (25), large amounts of MMTV RNA, and extra MMTV provirus DNA copies (24).In this report we show that GR mouse T-cell leukemias contain the extra MMTV proviral DNA derived from the endogenous MMTV provirus of Mtv-2 and that the leukemias are clonal with respect to the acquired MMTV provirus. We also found that rearrangements have occurred in the LTRs of all the extra MMTV proviruses, but different * C...

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Mammary tumor induction loci in GR and DBAf mice contain one provirus of the mouse mammary tumor virus

Cited by 97 publications

References 25 publications

Hormone-responsive expression of an endogenous proviral gene of mouse mammary tumor virus after molecular cloning and gene transfer into cultured cells.

Hormone-responsive expression of an endogenous proviral gene of mouse mammary tumor virus after molecular cloning and gene transfer into cultured cells.

MMTV-induced mammary tumorigenesis: gene discovery, progression to malignancy and cellular pathways

Rearrangements in the long terminal repeat of extra mouse mammary tumor proviruses in T-cell leukemias of mouse strain GR result in a novel enhancer-like structure.

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