Postdoctoral Fellow Program Research Publications

First Example

Park KJ, Krishnan V, O-Malley BW, Yamamoto Y, Gaynor RB. Formation of an IKKalpha-dependent transcription complex is required for estrogen receptor-mediated gene activation. Molecular Cell, 2005 Apr 1;18(1):71-82.

Abstract
The IκB kinases IKKα and IKKβ regulate distinct cytoplasmic and nuclear events that are critical for cytokine-mediated activation of the NF-κB pathway. Because the IKKs have previously been demonstrated to associate with the nuclear hormone receptor coactivator AIB1/SRC-3, the question of whether either IKKα or IKKβ may be involved in increasing the expression of hormone-responsive genes was addressed. We demonstrated that IKKα, in conjunction with ERα and AIB1/SRC-3, is important in activating the transcription of estrogen-responsive genes, including cyclin D1 and c-myc, to result in the enhanced proliferation of breast cancer cells. Estrogen treatment facilitated the association of IKKα, ERα, and AIB1/SRC-3 to estrogen-responsive promoters and increased IKKα phosphorylation of ERα, AIB1/SRC-3, and histone H3. These results suggest that IKKα plays a major role in regulating the biological effects of estrogen via its promoter association and modification of components of the transcription complex.

Read More

Second Example

Yan, Jiangli et al. Complete Relative Stereochemistry of Multiple Stereocenters Using Only Residual Dipolar Couplings. Journal of the American Chemical Society. 126(15). April 21, 2004. 5008-5017.

Abstract
Residual dipolar couplings (RDCs), in combination with molecular order matrix calculations, were used to unambiguously determine the complete relative stereochemistry of an organic compound with five stereocenters. Three simple one-dimensional experiments were utilized for the measurements of 13C-1H, 13C-19F, 19F-1H, and 1H-1H RDCs. The order matrix calculation was performed on each chiral isomer independently. The fits were evaluated by the comparison of the root-mean-square deviation (rmsd) of calculated and measured RDCs. The order tensor simulations based on two different sets of RDC data collected with phage and bicelles are consistent. The resulting stereochemical assignments of the stereocenters obtained from using only RDCs are in perfect agreement with those obtained from the single-crystal X-ray structure. Six RDCs are found to be necessary to run the simulation, and seven are the minimum to get an acceptable result for the investigated compound. It was also shown that 13C-1H and 1H-1H RDCs, which are the easiest to measure, are also the most important and information-rich data for the order matrix calculation. The effect of each RDC on the calculation depends on the location of the corresponding vector in the structure. The direct RDC of a stereocenter is important to the configuration determination, but the configuration of stereocenters devoid of protons can also be obtained from analysis of nearby RDCs.

Read More

Third Example

Quirk JC, Siuda ER, Nisenbaum ES. Molecular determinants responsible for differences in desensitization kinetics of AMPA receptor splice variants. J Neurosci. 2004 Dec 15;24(50):11416-20.

Abstract
Flip (i) and flop (o) alternatively spliced variants of the four glutamate AMPA receptor subunits (GluR1-4) are differentially expressed in the CNS and can display distinct rates of desensitization that contribute to the heterogeneity of native AMPA receptor-dependent synaptic responses. In the present study, we initially compared the kinetics of desensitization in response to fast application of glutamate (1 mM) for the eight different homomeric recombinant human AMPA receptors (hGluR1-4i and o) heterologously expressed in mammalian cells. Consistent with previous reports on recombinant rat AMPA receptors, the time constants of desensitization between human GluR1i and GluR1o receptors were the same, whereas the flip isoforms for GluR2-4 receptors exhibited significantly slower rates of desensitization compared with the flop isoforms. To identify the molecular determinants responsible for these functional differences, the effects of exchanging amino acid residues in the flip-flop cassette of GluR2i and GluR2o were investigated. Three amino acid residues in the flip-flop region (Thr765, Pro766, and Ser775 in flip and Asn765, Ala766, and Asn775 in flop) were identified that contribute to splice-variant differences in the rate of desensitization. Recent structural data show that these three residues are located on helix J, which forms part of the intradimer interface of AMPA receptor ligand-binding cores, and that the stability of this interface may regulate desensitization. The present results suggest that these three residues may confer differences in flip and flop receptor desensitization rates by directly and/or indirectly influencing the stability of the interface between adjacent subunits.

Read More