The tumor suppressor protein p53 induces cell cycle arrest or apoptosis in response to DNA damage. Loss-of-function mutations of the p53 gene is found in up to 50% of tumors. It has been suggested that wildtype p53 may play a role in DNA repair and that expression of mutant forms of p53 may alter cellular resistance to the DNA damage caused by gamma-radiation. Furthermore, p53 had been thought to function as a cell cycle checkpoint. Expression profiling of purified mouse gonadal somatic cells during the critical time window of sex determination reveals novel candidate genes for human sexual dysgenesis syndromes Beverdam A, et al.
NCBI Summary:
Tumor protein p53, a nuclear protein, plays an essential role in the regulation of cell cycle, specifically in the transition from G0 to G1. It is found in very low levels in normal cells, however, in a variety of transformed cell lines, it is expressed in high amounts, and believed to contribute to transformation and malignancy. p53 is a DNA-binding protein containing DNA-binding, oligomerization and transcription activation domains. It is postulated to bind as a tetramer to a p53-binding site and activate expression of downstream genes that inhibit growth and/or invasion, and thus function as a tumor suppressor. Mutants of p53 that frequently occur in a number of different human cancers fail to bind the consensus DNA binding site, and hence cause the loss of tumor suppressor activity. Alterations of the TP53 gene occur not only as somatic mutations in human malignancies, but also as germline mutations in some cancer-prone families with Li-Fraumeni syndrome.
General function
Cell death/survival, Apoptosis, Cell cycle regulation, DNA Replication, Tumor suppressor, Nucleic acid binding, DNA binding, Transcription factor
Comment
The apoptosis regulators, Bcl-2 and Bax, are transcriptional targets for p53. P53 induces the proapoptotic Bax gene to induce apoptosis (Gomez-manzano et al., 1999)./////SUMOylation of Mouse p53b by SUMO-1 Promotes Its Pro-Apoptotic Function in Ovarian Granulosa Cells. Liu XM et al. Follicular atresia is a process of spontaneous degradation of follicles, hindering growth and development in the mammalian ovary. Previous studies showed that follicular atresia was caused by apoptosis of granulosa cells, for which a number of apoptosis-related genes have already been identified. The roles of p53 in apoptosis of mouse granulosa cells and its post-translational modification are still unclear. The main objective of this study was to explore the roles of p53 in mouse granulosa cells. We found that mouse p53b, but not p53a, could be SUMOylated by SUMO-1 at lysine 375, which was essential for the protein stability of p53b in a dose-dependent manner. Immunofluorescent staining showed that wild p53b was located in the nucleus of granulosa cells, while its mutation of SUMOylated site (K375R) was localized in both nucleus and cytoplasm, implying that SUMOylation was necessary for the nuclear localization of p53b in granulosa cells. Overexpression of wild-type p53b, but not the mutation of SUMOylation site (K375R), significantly induced the expression of apoptosis-related gene, Bax, and increased the level of apoptosis in granulosa cells. This suggested that SUMO-1 modification of p53b was essential for inducing apoptosis in granulosa cells. Our results provide strong evidences that modification of p53b by SUMO-1 at lysine 375 was necessary for its activity to induce apoptosis in mouse granulosa cells, and it was involved in the regulation of p53b protein stability and nuclear localization. This implies that modification of p53b by SUMO-1 might regulate follicular atresia by inducing the apoptosis of ovarian granulosa cells in mice.
Keren-Tal et al. (1995) demonstrate that wild-type p53 can cooperate with cAMP-generated signals in the induction of steroidogenesis and programmed cell death in granulosa cells. Kim et al. (1999) demonstrated an increase in p53 immunostaining in granulosa cells of atretic follicles.
Influence of p53 and genetic background on prenatal oogenesis and oocyte attrition in mice. Ghafari F et al. BACKGROUND Meiotic progression, and the number of oocytes surviving to birth, determine the ovarian reserve, yet the control of prenatal oogenesis is poorly understood. We investigated the effects of genetic background and p53 upon oogenesis in mice. METHODS Fetal and neonatal ovaries were analysed in B6CBf1 and B6CBf2 mice from 15.5 to 21 days post-coitum (dpc) and p53 (a tumour suppressor gene) knockout, heterozygous and wild-type mice from 15.5 to 16 dpc. Oocytes in meiotic prophase I (MPI) were identified by labelling synaptonemal complex protein 3, and the specific stage of MPI was classified by the appearance of axial elements. Apoptosis and DNA breaks were assessed by cleaved poly-(ADP-ribose) polymerase (PARP-1) and terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling (TUNEL), respectively. RESULTS The leptotene, zygotene and pachytene stages were earlier in f1 than f2 generations with significant differences at all stages (PCherian-Shaw M, et al reported the regulation of steroidogenesis by p53 in macaque granulosa cells and H295R human adrenocortical cells.
Transcription factor p53 can regulate proliferation, apoptosis and secretory activity of luteinizing porcine ovarian granulosa cell cultured with and without ghrelin and FSH. Sirotkin A et al. The aim of our in vitro experiments was to examine the role of transcription factor p53 in controlling the basic functions of ovarian cells and their response to hormonal treatments. Transfection with the p53 gene construct promoted accumulation of this transcription factor within cells. It also stimulated the expression of marker of apoptosis (ASK-1). Over-expression of p53 resulted in reduced accumulation of marker of proliferation (cyclin B1), P4 and PGF secretion and increased OT and PGE secretion. Ghrelin, when added alone, did not affect p53 or P4, but reduced ASK-1 and increased PGF and PGE secretion. Over-expression of p53 reversed the effect ghrelin on OT, caused it to be inhibitory to P4 secretion, but did not modify its action on ASK-1, PGF or PGE. FSH promoted the accumulation of p53, ASK-1 and cyclin B1; these effects were unaffected by p53 transfection. These multiple effects of the p53 gene construct on luteinizing granulosa cells, cultured with and without hormones (1) demonstrate the effects of ghrelin and FSH on porcine ovarian cell apoptosis and secretory activity, (2) confirm the involvement of p53 in promoting apoptosis and inhibiting P4 secretion in these cells, (3) provide the first evidence, that p53 suppress proliferation of ovarian cells, (4) provide the first evidence that p53 is involved in the control of ovarian peptide hormone (OT) and prostaglandin (PGF and PGE) secretion, and (5) suggest that p53 can modulate, but probably not mediate the effects of ghrelin and FSH on the ovary.
Expression regulated by
LH
Comment
Regulation of steroidogenesis by p53 in macaque granulosa cells and H295R human adrenocortical cells Cherian-Shaw M, et al .
Ovulation and formation of a functional corpus luteum in primates involve cascades of events, including increased progesterone synthesis and changes in granulosa cell proliferation. However, critical gaps remain in our understanding of how an ovulatory gonadotropin surge initiates these processes. To more fully elucidate changes in the cell cycle during luteal formation, the actions of the tumor suppressor p53 were examined. Rhesus macaque granulosa cells were isolated during controlled ovarian stimulation protocols before (nonluteinized) or after (luteinized) an ovulatory gonadotropin stimulus. Phosphorylated p53 protein was detected in the cytoplasm of granulosa cells before and after human chorionic gonadotropin (hCG) treatment, whereas granulosa cells from hormonally controlled rats did not express p53 before or after hCG. Treatment of nonluteinized macaque granulosa cells with hCG and the p53 inhibitor pifithrin-alpha (PFT) in vitro did not alter markers of the cell cycle, including proliferating cell nuclear antigen, p21, and human double minute (HDM)-2 expression compared with hCG alone. Levels of pregnenolone and progesterone increased 2- and 4-fold, respectively, within 6 h of hCG treatment, whereas PFT completely blocked this hCG-induced effect. Estradiol was increased transiently (>10-fold) by hCG plus PFT relative to levels after hCG alone. PFT also inhibited hCG-induced increases in steroidogenic acute regulatory protein and 3beta-hydroxysteroid dehydrogenase mRNAs. Similar results were obtained using the human adrenocortical cell line H295R, suggesting that p53 may have a general function in primate steroidogenesis. These data indicate that p53 plays a key role in luteinization of the primate ovarian follicle though the regulation of steroidogenic enzymes leading to progesterone synthesis.
Ovarian localization
Granulosa, Luteal cells, Surface epithelium
Comment
Immunohistochemical analysis revealed that p53
protein was localized exclusively to nuclei of apoptotic granulosa cells of atretic follicles (Tilly et al., 1995).
Ovotoxic Effects of Galactose Involve Attenuation of Follicle-Stimulating Hormone Bioactivity and Up-Regulation of Granulosa Cell p53 Expression. Banerjee S et al. Clinical evidence suggests an association between galactosaemia and premature ovarian insufficiency (POI); however, the mechanism still remains unresolved. Experimental galactose toxicity in rats produces an array of ovarian dysfunction including ovarian development with deficient follicular reserve and follicular resistance to gonadotrophins that characterize the basic tenets of human POI. The present investigation explores if galactose toxicity in rats attenuates the bioactivity of gonadotrophins or interferes with their receptor competency, and accelerates the rate of follicular atresia. Pregnant rats were fed isocaloric food-pellets supplemented with or without 35% D-galactose from day-3 of gestation and continuing through weaning of the litters. The 35-day old female litters were autopsied. Serum galactose-binding capacity, galactosyltransferase (GalTase) activity, and bioactivity of FSH and LH together with their receptor competency were assessed. Ovarian follicular atresia was evaluated in situ by TUNEL. The in vitro effects of galactose were studied in isolated whole follicles in respect of generation of reactive oxygen species (ROS) and expression of caspase 3, and in isolated granulosa cells in respect of mitochondrial membrane potential, expression of p53, and apoptosis. The rats prenatally exposed to galactose exhibited significantly decreased serum GalTase activity and greater degree of galactose-incorporation capacity of sera proteins. LH biopotency and LH-FSH receptor competency were comparable between the control and study population, but the latter group showed significantly attenuated FSH bioactivity and increased rate of follicular atresia. In culture, galactose increased follicular generation of ROS and expression of caspase 3. In isolated granulosa cells, galactose disrupted mitochondrial membrane potential, stimulated p53 expression, and induced apoptosis in vitro; however co-treatment with either FSH or estradiol significantly prevented galactose-induced granulosa cell p53 expression. We conclude that the ovotoxic effects of galactose involves attenuation of FSH bioactivity that renders the ovary resistant to gonadotrophins leading to increased granulosa cell expression of p53 and follicular atresia.
Follicle stages
Antral, Corpus luteum
Comment
Patterns of p53 ribonucleic acid expression in the corpus luteum suggest that the protein products of p53 and bcl-2 do not act in a diametric manner to regulate programmed cell death in the corpus luteum (Trott et al., 1997).
Phenotypes
Mutations
1 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: fertile Comment: Transgenic mice lacking the p53 tumor suppressor gene are indistinguishable from their wildtype litter mates except for their dramatically early onset of tumor formation. Donehower et al. (1992) showed that although development was normal in mice lacking one or both alleles of p53 as a result of gene targeting of ES cells, spontaneous tumors, specifically lymphomas and sarcomas, occurred in high frequency.