Androgen and progesterone receptors (AR and PR) are two determining factors in gonadal differentiation that are highly expressed in developing and mature gonads. Loss of AR results in XY sex reversal and mutations causing reduced AR activity lead to varying degrees of defects in masculinization. Female PR knockout mice are infertile due to ovarian defects. While much has been discovered about positive regulation of these receptors by coactivators little is known about repression of the transcriptional activity of AR and PR in the presence of agonists. In this study we assessed the effect of SMRT and DAX-1 on AR and PR activity in the presence of both agonists and partial antagonists. We show that SMRT and DAX-1 repress agonist-dependent activity of both receptors, and the mechanism of repression includes disruption of the receptor dimer interactions rather than recruitment of histone deacetylases. We demonstrate that endogenous agonist-bound PR and DAX-1 in T47D breast cancer cells and endogenous AR and DAX-1 in LNCaP prostate cancer cells can be coimmunoprecipitated suggesting that the interaction is physiological. Surprisingly, although DAX-1 represses partial antagonist activity of AR, it was ineffective in repressing partial antagonist induced activity of PR. In contrast to most reported repressors, the expression of DAX-1 is restricted. We found that although DAX-1 is expressed in normal human prostate, its expression is strongly reduced in benign prostatic hyperplasia suggesting that DAX-1 plays a role in limiting AR activity in prostate.Nuclear receptors are regulated both by coactivators and by corepressors. Although steroid receptor coactivators have been studied extensively, less is known about corepressors of agonist activated steroid receptors. Androgens, acting through AR, 1 play a role in both benign prostatic hyperplasia (BPH) and prostate cancer. In both cases, reduction in AR activity is an important component of treatment, although fully effective treatments are not yet available. Two well characterized corepressors of thyroid receptor (TR) activity, NCoR (nuclear receptor co-repressor) and SMRT (silencing mediator for retinoid acid receptor (RAR) and TR), have been identified previously (1, 2). They appear to work through binding to TR aporeceptor, recruiting complexes containing histone deacetylases (HDACs); they dissociate from the receptor upon agonist binding allowing coactivator complexes to form (3). In the case of estrogen receptor (ER), these repressors interact with the antagonist bound receptor through a region that largely overlaps with the coactivator binding interface, and recruit HDACs (4). An orphan nuclear receptor DAX-1 (dosage sex reversal, adrenal hypoplasia congenita critical region on the X chromosome, gene 1) has been reported to inhibit steroidogenic factor 1 (SF-1) and ER activity (5, 6). DAX-1 is an atypical nuclear receptor containing an ssDNA/RNA binding domain in its N terminus and a multihelical C-terminal domain, a putative ligand binding domain (LBD) (7). DAX-1 i...

To evaluate the role of fine-needle aspiration (FNA) biopsy of thyroid nodules in pediatric and adolescent patients, the cytology reports of 218 thyroid FNA biopsies performed on children and adolescents ranging from 10 to 21 yr of age were reviewed. The cytology diagnoses were categorized into four groups: unsatisfactory, benign, suspicious, and malignant. One hundred nineteen (54%) of the aspirates were diagnosed as "benign," 20 (9%) were diagnosed as suspicious for malignancy; and 17 (8%) were diagnosed as malignant. Sixty-two (28%) of the aspirates were read as unsatisfactory for interpretation. Sensitivity of thyroid FNA in diagnosing thyroid malignancy relative to final histological diagnoses was 100%, and specificity was 65%. FNA of thyroid nodules in the pediatric and adolescent population is comparably as sensitive and specific as in the adult population. The acceptance of this procedure in the routine evaluation of young patients' thyroid nodules should reduce the number of unnecessary surgeries for benign thyroid disease.

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