Lisa Gentile

The highly conserved beta-hairpin of the paired DNA-binding domain is required for assembly of Pax-Ets ternary complexes.

ABSTRACT Pax family transcription factors bind DNA through the paired domain. This domain, which is comprised of two helix-turn-helix motifs and a β-hairpin structure, is a target of mutations in congenital disorders of mice and humans. Previously, we showed that Pax-5 (B-cell-specific activator protein) recruits proteins of the Ets proto-oncogene family to bind a composite DNA site that is essential for efficient transcription of the early-B-cell-specificmb-1 promoter. Here, evidence is provided for specific interactions between Ets-1 and the amino-terminal subdomains of Pax proteins. By tethering deletion fragments of Pax-5 to a heterologous DNA-binding domain, we show that 73 amino acids (amino acids 12 to 84) of its amino-terminal subdomain can recruit the ETS domain of Ets-1 to bind the composite site. Furthermore, an amino acid (Gln22) within the highly conserved β-hairpin motif of Pax-5 is essential for efficient recruitment of Ets-1. The ability to recruit Ets proteins to bind DNA is a shared property of Pax proteins, as demonstrated by cooperative DNA binding of Ets-1 with sequences derived from the paired domains of Pax-2 and Pax-3. The strict conservation of sequences required for recruitment of Ets proteins suggests that Pax-Ets interactions are important for regulating transcription in diverse tissues during cellular differentiation.

Identification of a neurosteroid binding site contained within the GluR2-S1S2 domain.

Glutamate receptors play a major role in neural cell plasticity, growth, and maturation. The degree to which ionotropic glutamate receptors (iGluR) conduct current is dependent on binding of extracellular ligands, of which glutamate is the native agonist. Although the glutamate binding site of the GluR2 class of amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) iGluR has been structurally characterized, the allosteric sites attributed to neurosteroid binding have yet to be localized. Here, using intrinsic tryptophan fluorescence spectroscopy, we show that the extracellular glutamate binding core of the GluR2 class of AMPA receptors also binds to two neurosteroids, pregnenolone sulfate (PS) and 3α-hydroxy-5β-pregnan-20-one sulfate, both of which negatively modulate its activity. Interest in these sulfated neurosteroids stems from their differential modulation of other members of the iGluR family and their potential use as endogeneous agents for stroke therapy. In particular, whereas PS inhibits AMPA and other non-N-methyl-d-aspartate (NMDA) family members, it activates the NMDA receptor. In addition to providing evidence for binding of these neurosteroids to the glutamate binding core of the GluR2 class of AMPA receptors, our data suggests that both neurosteroids bind in a similar manner, consistent with their modulation of activity of this class of iGluR. Interestingly, the conformational change induced upon binding of these neurosteroids is distinct from that induced upon glutamate binding.

Assigning the NMR spectra of aromatic amino acids in proteins: analysis of two Ets pointed domains

The measurement of interproton nuclear Overhauser enhancements (NOEs) and dihedral angle restraints of aromatic amino acids is a critical step towards determining the structure of a protein. The complete assignment of the resonances from aromatic rings and the subsequent resolution and identification of their associated NOEs, however, can be a difficult task. Shown here is a strategy for assigning the 1H, 13C, and 15N signals from the aromatic side chains of histidine, tryptophan, tyrosine, and phenylalanine using a suite of homo- and hetero-nuclear scalar and NOE correlation experiments, as well as selective deuterium isotope labelling. In addition, a comparison of NOE information obtained from homonuclear NOE spectroscopy (NOESY) and 13C-edited NOESY-heteronuclear single quantum correlation experiments indicates that high-resolution homonuclear two-dimensional NOESY spectra of selectively deuterated proteins are invaluable for obtaining distance restraints to the aromatic residues.

Antidepressant Interactions with the NMDA NR1-1b Subunit

The targets for tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and selective norepinephrine reuptake inhibitors (SNRIs) are known to be the serotonin and norepinephrine transport (reuptake) proteins which are embedded in presynaptic nerve terminals and function to bring these neurotransmitters from the synaptic cleft back into the presynaptic neuron. Using a combination of intrinsic and extrinsic fluorescence quenching, Stern-Volmer analysis, and protease protection assays, we have shown that therapeutics from each of these three classes of antidepressants bind to the extracellular S1S2 domain of the NR1-1b subunit of the NMDA receptor. These results are in agreement with recent work from our lab demonstrating the interaction of antidepressants with the S1S2 domain of the GluR2 subunit of the AMPA receptor, another member of the ionotropic glutamate receptor subfamily, as well as work from other labs, and continue the discussion of the involvement of ionotropic glutamate receptors in depression.

Letter to the Editor: Chemical shift and secondary structure conservation of the PNT/SAM domains from the Ets family of transcription factors

The DNA-binding ETS domain defines the Ets familyof transcription factors. A subset of this family, in-cluding Ets-1, Ets-2, GABPα, Erg, Fli-1 and Tel, alsoshare a conserved Pointed (PNT) or SAM domain thatmay functionin oligomerization,MAP kinase dockingor association with other regulatory proteins. The so-lution structure of the PNT/SAM domain from Ets-1(PDB: 1qbv; Slupsky et al., 1998a) has an architec-ture of a core four α-helical bundle interfaced withan additional N-terminal helix. In contrast, the crystalstructure of the homologous domain from Tel (1ji7;Kim et al., 2001) shows only the four core helices, asalso seen in the structures of SAM domains from non-Ets family memberssuch as p73 (1cok), polyhomeotic(1kw4) and the Ephrin receptors (1b4f, 1sgg, 1b0x).The additional N-terminal helix present in Ets-1 is anintegral part of the structured PNT/SAM domain asevident by