Our Science – Miller Website
Maria Miller, Ph.D.
For over 30 years I have been taking part in the structure determination, biophysical characterization, and analysis of a number of biologically important macromolecules. Some of main achievements include: (1) analysis of conformers, design, and crystal structure determination of a DNA duplex with unpaired bases; (2) the first crystal structure of a retroviral protease and the first structure of the protease from HIV-1 virus complexed with an inhibitor; (3) modeling studies of macrophage stimulating protein that helped to establish major determinants of its binding to the receptor and the mode of receptor dimerization by plasminogen related growth factors. I also studied the effects of oncogenic mutations on the structure and stability of MET and VHL proteins. Recently, my research has been focused on intermolecular interactions involved in transcription.
Structural studies of C/EBP transcriptional activators. (Collaboration with Dr. P. Johnson, Laboratory of Cancer Prevention, NCI). CCAAT/enhancer binding proteins (C/EBPs) regulate cell growth, differentiation, and survival but can also contribute to tumorigenesis and viral diseases. C/EBPβ is considered to be a promising therapeutic target in epithelial tumors. We use x-ray crystallography, modeling and bioinformatic tools to gain insights into molecular mechanisms regulating biological activities of C/EBP proteins. Sequence analysis indicated that C/EBPbeta is a natively unstructured protein able to change conformation upon binding to molecular partners. We proposed a model of the auto-inhibited form and identified several novel phosphorylation dependent protein recognition motifs for PTIP, Plks and Pin1. Previously, we determined structure of C/EBPalpha bound to its cognate DNA. The major current goals are to determine the structural basis for interactions of C/EBP proteins with the transcriptional coactivators: histone acetyltransferase p300 and histone methylation regulator, PTIP.
The structure of the Taz2 domain of p300 and its interactions with transcription factors. CBP and its paralogue p300 are histone acetyl transferases that regulate gene expression by interacting with multiple transcription factors via specialized domains. Taz2 domain binds specifically to acidic transactivating domains (TADs) of several TFs that include p53 tumor suppressor, ETF2, and members of the STAT and C/EBP families. C/EBPs binding results in massive phosphorylation of the C-terminal part of p300/CBP. We determined the crystal structure of a segment of human p300 protein corresponding to the extended zinc-binding Taz2 domain. Based on the analysis of crystal contacts and molecular modeling we proposed a hypothetical model of the binding of phosphorylated p53 peptide to Taz2. The interactions between the minimal TAD of C/EBPepsilon and human p300 Taz2 were determined from the crystal structure of the chimera protein composed of p300 Taz2 (residues 1723-1818) and C/EBPepsilon (residues 37-61). We propose a model of C/EBPbeta binding to Taz2 that suggests that phosphorylation of p300 is executed by kinases which dock to sites located N-terminally to its minimal TAD. In collaboration with Dr. E. Appella (LCB, NCI) we were also investigating the effect of site-specific phosphorylation on the binding affinity to p300 for a number of peptides derived from the TADs of the p53.
Structural studies of intermolecular interactions mediated by histone methylation regulator PTIP. Pax2 transactivation domain interacting protein (PTIP) is a ubiquitously expressed nuclear protein essential for embryonic development. PTIP mediates assembly of H3K4 methyltransferase (HMT) complex that methylates Lys4 on histone H3 at specific DNA sequences. It has been thereby implicated in transcriptional regulation and independently in DNA damage repair. Both activities are required for immunoglobulin class switch recombination (CSR) and PTIP has been recently indicated as critical factor in development of mature B cells. PTIP regulates the expression of PPARgamma and C/EBPalpha during adipogenesis and it is also necessary for maintaining the correct epigenetic pattern in terminally differentiated cells. PTIP was discovered as Pax2 interacting protein; however, due to its role in histone methylation in a locus and tissue dependent manner, it is likely to interact with many other sequence specific DNA-binding proteins. Currently, there is no structural information of PTIP. PTIP contains two BRCT domains at the N-terminus and four (two closely apposed pairs) at the C-terminus. The most extreme C-terminal pair, BRCT 5-6, was shown in vitro to specifically bind to phosphoserine/threonine containing motifs (pS/TXXF/I/L). However, all four C-terminal BRCT domains are necessary for binding to phosphorylated p53BP1 and TGFβ-activated SMAD2. To elucidate the structural basis of phospho-epitopes recognition by PTIP we have undertaken x-ray crystallographic studies of the C-terminal BRCT domains in complex with phosphorylated peptides derived from p53BP1 and members of C/EBP family.
This page was last updated on 2/27/2013.