The tumor antigens simian virus 40 small t antigen (ST) and polyomavirus small and medium T antigens mediate cell transformation in part by binding to the structural A subunit of protein phosphatase 2A (PP2A). The replacement of B subunits by tumor antigens inhibits PP2A activity and prolongs phosphorylationdependent signaling. Here we show that ST mediates PP2A A/C heterodimer transfer onto the ligand-activated androgen receptor (AR). Transfer by ST is strictly dependent on the agonist-activated conformation of AR, occurs within minutes of the addition of androgen to cells, and can occur in either the cytoplasm or the nucleus. The binding of ST changes the conformation of the A subunit, and ST rapidly dissociates from the complex upon PP2A A/C heterodimer binding to AR. PP2A is transferred onto the carboxyl-terminal half of AR, and the phosphatase activity is directed to five phosphoserines in the amino-terminal activation function region 1, with a corresponding reduction in transactivation. Thus, ST functions as a transfer factor to specify PP2A targeting in the cell and modulates the transcriptional activity of AR.The nuclear receptor (NR) superfamily of ligand-activated transcription factors directs the expression of genes that control a wide range of processes, including development, metabolism, and reproductive biology (24). NRs such as the androgen receptor (AR) reside initially in the cytoplasm, where they bind their cognate ligand, undergo chaperone-assisted conformational changes, engage with the nuclear import machinery, and translocate to the nucleus (8). NRs undergo sequencespecific binding to response element DNAs and recruit regulatory proteins to enhancers and promoters of target genes en route to assembling preinitiation complexes, attracting RNA polymerase II, and initiating transcription (14). There is recent evidence that NR recruitment of regulatory proteins needed for transcription occurs in an ordered and cyclical fashion (25).Members of the NR superfamily have a modular structure consisting of an N-terminal domain, a central DNA binding domain (DBD), a flexible hinge region, and a C-terminal ligand-binding domain (LBD) (10). The AR makes contact with regulatory proteins through subdomains with activation functions in the N-terminal domain activation function region 1 (AF-1) and the C-terminal LBD (AF-2). The AR DBD mediates binding to androgen response element DNA, which contains two palindromic hexanucleotide half-sites separated by a three-nucleotide spacer. The AR LBD forms the ligand-binding pocket, provides binding sites for heat shock proteins, and mediates intramolecular interactions with the N-terminal domain (17, 31).Ligand binding is the primary mechanism for controlling the transactivation of NRs, and for some steroid hormone receptors, including AR, ligand binding controls subcellular localization as well (2). There is, however, a growing body of evidence that NR activity can be regulated by posttranslational modification. The phosphorylation of NRs can regulate ligand sensiti...

Here we report that mutations within the DNA-binding domain of AR, shown previously to inhibit nuclear export to the cytoplasm, cause an androgen-dependent defect in intranuclear trafficking of AR. Mutation of two conserved phenylalanines within the DNA recognition helix (F582, 583A) results in androgen-dependent arrest of AR in multiple subnuclear foci. A point mutation in one of the conserved phenylalanines (DeltaF582, F582Y) is known to cause androgen insensitivity syndrome (AIS). Both AIS mutants (DeltaF582, F582Y) and the export mutant (F582, 583A) displayed androgen-dependent arrest in foci, and all three mutants promoted androgen-dependent accumulation of the histone acetyl transferase CREB binding protein (CBP) in the foci. The foci correspond to a subnuclear compartment that is highly enriched for the steroid receptor coactivator glucocorticoid receptor-interacting protein (GRIP)-1. Agonist-bound wild-type AR induces the redistribution of GRIP-1 from foci to the nucleoplasm. This likely reflects a direct interaction between these proteins because mutation of a conserved residue within the major coactivator binding site on AR (K720A) inhibits AR-dependent dissociation of GRIP-1 from foci. GRIP-1 also remains foci-associated in the presence of agonist-bound F582, 583A, DeltaF582, or F582Y forms of AR. Two-dimensional phospho-peptide mapping and analysis with a phospho-specific antibody revealed that mutant forms of AR that arrest in the subnuclear foci are hypophosphorylated at Ser81, a site that normally undergoes androgen-dependent phosphorylation. Our working model is that the subnuclear foci are sites where AR undergoes ligand-dependent engagement with GRIP-1 and CBP, a recruitment step that occurs before Ser81 phosphorylation and association with promoters of target genes.

Our study shows a decrease in perceived difficulty and a concomitant increased ability to cannulate a vein using US versus traditional landmark guidance techniques, even in the novice phlebotomist.

The use of US guidance to assist in lumbar punctures did not improve the procedural success rate over traditional landmark techniques in an academic setting with novice providers. Although using US for procedural guidance significantly decreased the number of attempts, it seemed to have no effect on postprocedural pain or the time to obtain CSF.