ABSTRACT
The inheritance of one defective BRCA1 or BRCA2 allele predisposes an individual to developing breast and ovarian cancers. BRCA1 is a multifunctional tumor suppressor protein, which through interaction with a vast array of proteins has implications in processes such as cell cycle, transcription, DNA damage response and chromatin remodeling. Conversely, the oncogene, cyclin D1 is overexpressed in about 35% of all breast cancer cases. In this study, we provide detailed analyses on the phosphorylation state of BRCA1 by cyclin D1/cdk4 complexes. In particular, we have identified Ser 632 of BRCA1 as a cyclin D1/cdk4 phosphorylation site in vitro. Using chromatin immunoprecipitation assays, we observed that the inhibition of cyclin D1/cdk4 activity resulted in increased BRCA1 DNA binding at particular promoters in vivo. In addition, we identified multiple novel genes that are bound by BRCA1 in vivo. Collectively, these results indicate that cyclin D1/cdk4-mediated phosphorylation of BRCA1 inhibits the ability of BRCA1 to be recruited to particular promoters in vivo. Therefore, cyclin D1/Cdk4 phosphorylation of BRCA1 could provide a mechanism to interfere with the DNA-dependent activities of BRCA1.
Subject(s)
BRCA1 Protein/metabolism , Breast Neoplasms/metabolism , Cyclin D1/metabolism , Amino Acid Sequence , BRCA1 Protein/analysis , Breast Neoplasms/chemistry , Breast Neoplasms/genetics , Cell Cycle , Cell Line, Tumor , Chromatin Immunoprecipitation , Cyclin D1/analysis , Cyclin-Dependent Kinase 4/metabolism , DNA/metabolism , G1 Phase , Gene Expression Regulation, Neoplastic , Humans , Molecular Sequence Data , Phosphorylation , Promoter Regions, Genetic , Resting Phase, Cell CycleABSTRACT
Areca (betel) chewing is associated with the high incidence of oral squamous cell carcinoma (OSCC) and oral submucous fibrosis (OSF) in Asians. Heme oxygenase-1 (HO-1), encoding an oxidative response protein, plays protective roles in cells. A (GT)n microsatellite repeat in HO-1 promoter shows polymorphisms and modulates the level of gene transcription. We examined allelotypic frequencies of (GT)n repeats in 83 controls, 147 OSCC and 71 OSF. All subjects were male areca chewers. Logistic regression was used to adjust the age confounding for odds ratio (OR). (GT)n repeat polymorphism was classified into short (S), medium (M) and long (L) alleles. The adjusted OR in OSCC subjects carrying L allelotype relative to S allelotype was 1.75. Buccal squamous cell carcinoma (BSCC) is the most common OSCC subset in areca chewers. L allelotype implied the risk of BSCC with adjusted OR of 2.05, whereas M allelotype appeared protective for non-BSCC with adjusted OR of 0.49. Our findings indicated that longer (GT)n repeat allele in HO-1 promoter is associated with the risks of areca-related OSCC, while the shorter (GT)n repeat allele may have protective effects for OSCC.
Subject(s)
Areca , Carcinoma, Squamous Cell/genetics , Heme Oxygenase (Decyclizing)/genetics , Mouth Neoplasms/genetics , Polymorphism, Genetic/genetics , Promoter Regions, Genetic/genetics , Carcinoma, Squamous Cell/enzymology , Carcinoma, Squamous Cell/pathology , Dinucleotide Repeats , Genetic Predisposition to Disease , Heme Oxygenase (Decyclizing)/metabolism , Heme Oxygenase-1 , Humans , Incidence , Male , Membrane Proteins , Microsatellite Repeats , Mouth Neoplasms/enzymology , Mouth Neoplasms/pathology , Plants, Toxic , Risk FactorsABSTRACT
Psychogenic dizziness is defined as recurring or persistent symptoms of balance dysfunction, inconsistent with organic vestibular disease as determined by history, clinical examination and pertinent investigations, and consistent with emotional origin. Of 1,335 patients seen in our dizziness clinic between January 1988 and August 1991, psychogenic dizziness was diagnosed in 180 (13.5%) patients. There were 67 men and 113 women aged from 12 to 77 years (mean age 40.2 years). The characteristics of psychogenic dizziness are: (1) continuous dizziness for long periods of time; (2) younger patients; (3) predominant female; (4) associated symptoms of panic attack, such as headache, breathlessness, nausea, sleep disturbance, paresthesias, anxiety and palpitation; (5) symptoms of aggravation due to stressful life events; (6) normal neurotological bedside examination; (7) hyperventilation reproduced accurately. The electronystagmographic results of 74 patients show normal bithermal caloric responses in 47 patients (63.5%), caloric hyperactivity in 21 patients (28.4%), canal paresis in four patients (5.4%), canal paresis with directional preponderance in two patients (2.7%), large random voluntary eye swings or severe blinking in 35 patients (47.3%), and spontaneous nystagmus (slow phase velocity < 6.5 degrees/s) in four patients (5.4%). There were 31 patients who consulted psychiatrists with diagnoses of anxiety (51.6%), depression (16.1%), insomnia (12.9%), psychosomatic disorder and adjustment disorder. Treatment of patients with psychogenic dizziness must be directed at the underlying anxiety. Psychiatric consultation is necessary.
