PubMed Health⌕ Search

Biomedical subjects

I Daar

Publications and source records attributed to I Daar.

8 recordsLinked to original sources
PubMed1992

pp39mos is associated with p34cdc2 kinase in c-mosxe-transformed NIH 3T3 cells.

We investigated the possible interactions between pp39mos and p34cdc2 kinase in NIH 3T3 cells transformed by c-mosxe. pp39mos is coprecipitated with p34cdc2 when using either anti-PSTAIR antibody or p13suc1-Sepharose beads. Likewise, p34cdc2 is coprecipitated with pp39mos when using anti-mos antibody. However, pp39mos was not present in histone H1 kinase-active p34cdc2 complexes precipitated with anti-p34cdc2 C-terminal peptide antibody even during metaphase of the cell cycle. The molar ratio of p34 to pp39mos in the p13suc1 complex is approximately 2:1. Consistent with the tight association between pp39mos and tubulin, tubulin was also present in equivalent amounts with pp39mos and p34 in the p13suc1 complex. This pp39mos-p34cdc2-tubulin complex may be important in transformation by the mos oncogene.

3T3 Cells↗
PubMed1991

The ras oncoprotein and M-phase activity.

The endogenous mos proto-oncogene product (Mos) is required for meiotic maturation. In Xenopus oocytes, the ras oncogene product (Ras) can induce meiotic maturation and high levels of M-phase--promoting factor (MPF) independent of endogenous Mos, indicating that a parallel pathway to metaphase exists. In addition, Ras, like Mos and cytostatic factor, can arrest Xenopus embryonic cell cleavage in mitosis and maintain high levels of MPF. Thus, in the Xenopus oocyte and embryo systems Ras functions in the M phase of the cell cycle. The embryonic cleavage arrest assay is a rapid and sensitive test for Ras function.

Animals↗
PubMed1991

A characterization of cytostatic factor activity from Xenopus eggs and c-mos-transformed cells.

In Xenopus oocytes, the mos proto-oncogene product is required during meiosis I for the activation of maturation promoting factor (MPF) and the subsequent breakdown of the germinal vesicle (GVBD). In addition, the mos product has been shown to be a candidate "initiator" of meiotic maturation and is an active component of cytostatic factor (CSF), an activity responsible for metaphase II arrest. Here we demonstrate that pp39mos is required throughout oocyte maturation. We found that in progesterone stimulated oocytes, depletion of mos RNA immediately before GVBD terminally decreased MPF. Likewise, oocytes depleted of mos RNA and induced to mature with crude MPF proceeded through GVBD but lacked the MPF activity required to arrest mature oocytes at metaphase II. Thus, during maturation the mos product is required, directly or indirectly, to sustain MPF activity. On the other hand, mouse NIH/3T3 cells transformed by the constitutive expression of pp39mosxc possessed CSF activity but lacked constitutive levels of MPF or its associated histone H1 kinase activity. Moreover, cytosols prepared from transformed NIH/3T3 cells or Xenopus eggs had similar levels of CSF activity, but pp39mos levels were greater than 40-fold higher in the transformed cell extract. These analyses show that maintenance of CSF during interphase does not result in the maintenance of MPF.

Animals↗
PubMed1991

mos gene transforming efficiencies correlate with oocyte maturation and cytostatic factor activities.

The mos proto-oncogenes from different vertebrate species transform mouse NIH 3T3 cells with markedly different efficiencies. v-mos, mouse (c-mosmu), and chicken (c-mosch) mos transform NIH 3T3 cells 10- to 100-fold more efficiently than do human (c-moshu) and Xenopus (c-mosxc) mos. The mos genes with the highest transforming activity efficiently induce maturation in Xenopus oocytes and mimic cytostatic factor (CSF) by causing mitotic cleavage arrest in embryos. Chimeric v-mos/c-moshu proteins that had high transforming efficiencies in NIH 3T3 cells were also effective in the induction of oocyte maturation and CSF cleavage arrest. We measured the in vitro autophosphorylation activities of the different mos proteins and found that the levels of kinase activity of v-mos, c-mosmu, and c-mosch were much higher than that of c-mosxc. These data indicate that mos gene transforming efficiency and the ability to induce oocyte maturation or mimic CSF activity are correlated with in vitro autophosphorylation activity and suggest that the mos protein plays a similar role in transformed cells and normal oocytes.

Animals↗
PubMed1990

mos proto-oncogene function.

Maturation promoting factor (MPF) is a cytoplasmic activity that causes oocytes arrested in prophase to resume meiosis. An inactive form of MPF termed pre-MPF exists in fully grown oocytes. In Xenopus oocytes, progesterone induces maturation and pre-MPF activation. These early maturation events require protein synthesis. We have shown that p39mos synthesis is rapidly induced in progesterone-treated Xenopus oocytes during the protein synthesis sensitive period and prior to activation of pre-MPF or germinal vesicle breakdown (GVBD). p39mos may qualify, therefore, as an 'initiator' of maturation. Mouse oocytes undergoing meiotic maturation also express p39mos. Microinjection of antisense mos oligodeoxynucleotides into fully grown mouse and Xenopus oocytes results in the block of meiotic maturation. In Xenopus, antisense-injected oocytes not only lack p39mos, but also lack MPF and fail to undergo GVBD. In the mouse, the microinjected oocytes progress through GVBD, but fail to produce the first polar body; cytogenetic analysis shows they are arrested at the bivalent chromosome stage of metaphase I. This and additional studies with Xenopus oocytes indicate that p39mos is also required throughout maturation. We have shown that p39mos is indistinguishable from the protein product constitutively expressed in NIH/3T3 cells transformed with activated c-mos. It is likely that its activity as a transforming gene may be due to activation of pre-MPF activities in interphase in the somatic cell cycle.

Animals↗
PubMed1990

Structure, tissue-specific expression, and transforming activity of the mouse met protooncogene.

A 6.7-kilobase met complementary DNA (cDNA) was isolated from a pcD cDNA library prepared from C3H mouse fibroblast cell line polyadenylated RNA. Sequence analysis of 6.7-kilobase met cDNA insert revealed that it contained the entire open reading frame and shared an overall homology of 88.1% with the human met gene. Using the mouse met cDNA as probe, high levels of met expression were observed in the kidney, brain, lung, skin, and embryonic tissue as well as in several factor responsive mouse myeloid cell lines. Under SV40 promoter control, the mouse met protooncogene cDNA in the pCD vector was able to transform NIH 3T3 cells. These transformed cells possess multiple copies of mouse met cDNA and exhibit properties of malignant cells, including growth in soft agar and induction of tumors in nude mice. Tumor explant cell lines analyzed by Western blot also reveal the presence of high levels of Mr 170,000 and 140,000 met protein product(s).

Amino Acid Sequence↗
PubMed1989

The product of the mos proto-oncogene as a candidate "initiator" for oocyte maturation.

The endogenous c-mos product, pp39mos, is required for progesterone-induced meiotic maturation in Xenopus oocytes. Treatment of oocytes with progesterone induced a rapid increase in pp39mos that preceded both the activation of maturation promoting factor (MPF) and germinal vesicle breakdown (GVBD). Microinjection of synthetic mos RNA into oocytes activated MPF and induced GVBD in the absence of progesterone. Thus, the mos proto-oncogene product may qualify as a candidate "initiator" protein of MPF and is at least one of the "triggers" for G2 to M transition.

Animals↗