The wild-type p53 gene product plays an important role in the control of cell proliferation, differentiation, and survival. Altered function is frequently associated with changes in p53 stability. We have studied the role of the ubiquitination pathway in the degradation of p53, utilizing a temperature-sensitive mutant, ts2O, derived from the mouse cell line BALB/c 3T3. We found that wild-type p53 accumulates markedly because of decreased breakdown when cells are shifted to the restrictive temperature. Introduction of sequences encoding the human ubiquitin-activating enzyme El corrects the temperature sensitivity defect in ts2O and prevents accumulation of p53. The data therefore strongly indicate that wild-type p53 is degraded intracellularly by the ubiquitinmediated proteolytic pathway.The nuclear phosphoprotein p53 is a negative regulator of cell proliferation and transformation (2,11,14). In many established cell lines and human cancers, the gene is mutated. Such mutations commonly result in a p53 which has increased stability and markedly altered function and have been the subject of several studies (30,31,38,57). Genetic instability indicated by gene amplification and impaired control of the G1-S transition in the cell cycle are exhibited by cells homozygous for p53 mutations (reviewed in reference 23). A role for p53 in transcriptional control is shown by sequence-specific DNA binding (4,15,26,28). Other studies have shown that wild-type p53 can affect expression of several genes and that specific binding of p53 to transcription factors, TATA-binding protein, and CCAAT-binding factor results in the altered transcription from the test promoters (1,51). An association between mdm2 protein and p53 has been established, and the mdm2 gene is known to undergo amplification in murine transformed cells and many human sarcomas (13,40,42). Transgenic mice with a complete loss of p53 protein develop normally but have a high frequency of tumors postnatally (10). Humans heterozygous for germ line p53 mutations have a high susceptibility to carcinogenesis (34).The mechanism by which p53 is regulated intracellularly is not completely understood, although it is widely accepted that turnover of the protein is an important aspect. Normally, p53 is a short-lived protein with a half-life of about 30 min (16,43,46). DNA tumor viruses express gene products which bind the normal p53 and alter its properties. In the case of human papillomavirus type 16, for example, the half-life of p53 is decreased in complexes with E6 and p53 (50), whereas complexes with simian virus 40 (SV40) large T protein and adenovirus ElB p55 result in an increased half-life of p53 (46,49). Mutations in SV40 large T protein which affect binding of p53 decrease the efficiency of SV40-mediated transformation of susceptible cells (32,35,56,63 (50) have shown that E6-p53 complexes generated in vitro are more rapidly degraded in reticulocyte extracts and that ubiquitinated intermediates can be detected. Under their experimental conditions, however, free p53 wa...

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It is uncertain whether uterine leiomyosarcoma arises de novo or in preexisting leiomyoma. Leiomyoma-like areas can be seen associated with uterine leiomyosarcoma, raising the possibility of precursor lesions for uterine leiomyosarcoma. In this study, we examined cases of uterine leiomyosarcoma associated with leiomyoma-like areas at the histological, immunohistochemical and DNA level to further evaluate if benignlooking leiomyoma-like and uterine leiomyosarcoma areas are related. Cases of uterine leiomyosarcoma observed at the New York University Medical Center from 1994 to 2007 were reviewed for the presence of leiomyoma-like areas. Of the 26 cases of uterine leiomyosarcoma observed during this period, 18 cases had an associated leiomyoma-like area (five cellular leiomyoma, four symplastic leiomyoma, four cellular and symplastic leiomyoma and five usual type leiomyoma). Sixteen of the 18 cases were examined immunohistochemically for Ki-67, for estrogen receptor, progesterone receptor and for p53. Immunohistochemical profiles were as expected for leiomyoma-like (the mean expression of p53, ER, PR and Ki-67 at 0.3, 63, 75 and 0.6%, respectively), symplastic leiomyoma-like areas (the mean expression of p53, ER, PR and Ki-67 at 0.6, 85, 89 and 5.5%, respectively) and uterine leiomyosarcoma areas (the mean expression of p53, ER, PR and Ki-67 at 52, 38, 39 and 61%, respectively). In six cases, the leiomyoma-like and uterine leiomyosarcoma areas from each case were examined using high-density oligonucleotide array-CGH to determine genetic aberrations in the two areas. Nearly all the genetic aberrations found in leiomyoma-like areas were also found in the corresponding uterine leiomyosarcoma areas. In addition, uterine leiomyosarcoma areas had additional genetic aberrations. The immunohistochemical profiles and genetic aberrations of the examined cases suggest that uterine leiomyosarcoma could arise from the preexisting leiomyoma-like areas that often have a symplastic or cellular morphology.

Children with ADHD possessing the DRD4 7R allele require higher doses of methylphenidate for symptom improvement and symptom normalization. This pharmacogenetic study demonstrates that the 7-repeat allele of the DRD4 gene VNTR polymorphism correlates with treatment outcomes.