Structural Biology of the Human High Mobility Group A (HMGA) Proteins: Characterizing the Hub of Nuclear Function
EMSL Project ID
7794
Abstract
Chromatin high mobility group protein (HMGA1) belongs to a family of nonhistone mammalian proteins that are thought to be important structural components affecting the conformation and function of chromatin. These proteins are also known as architectural transcription factors because of their ability to function as components of chromatin structure and as auxiliary gene transcription factors (Reeves, 2001). Over-expression of HMGA1 has been observed in different types of human cancers and it has been demonstrated that such over-expression inhibits the transcription of genes coding for several proteins involved in DNA repair including DNA ligase III, Dnase X, ATM and DNA methyltransferase. Thus, HMGA1 is also an oncoprotein. HMGA1 binds DNA, preferentially to the narrow minor groove of A?T rich segments. Circular dichroism and nuclear magnetic resonance studies indicate that HMGA1 lacks secondary or tertiary structure when free in solution. When HMGA1 binds to DNA a unique secondary structure referred to as an ?AT-hook? is induced in the DNA binding regions (Reeves & Nissen, 1990; Huth et al., 1997). The planar, crescent shaped AT-hooks have a consensus sequence of Pro-Arg-Gly-Arg-Pro with R-G-R-P being invariant. Each HMGA1 protein contains three similar but independent AT-hooks flanked on either side by a number of positively charged lysine and arginine residues. Our limited molecular level understanding of how HMGA1 regulates gene expression comes from a single structure of a truncated HMGA1 containing only two AT-hooks (HMGA51-90) bound to two different DNA dodecamers solved using NMR spectroscopy (Huth et al., 1997). The decision to work with truncated HMGA1 and short DNA was necessary at the time in order to simplify spectral complexity and to keep the molecular weight favorable for NMR studies. However, working with the truncated HMGA1 and short DNA has its shortcomings. For example, in the Huth structure (1997) each AT-hook in the HMGA protein bound to a different DNA molecule and the third AT-hook was absent altogether. There have been several advances in NMR technology since the earlier HMGA51-90 structure was published, including increases in field strength, more powerful NMR experiments and more versatile DNA and protein labeling capabilities, that make it possible to reexamine the full-length HMGA1 protein bound to a DNA molecule that is long enough that all three AT-hooks can bind to a single DNA promoter. To determine the effect that HMGA1 binding has on the structure of the DNA substrate, it will also be necessary to determine the structure of the DNA prior to HMGA1 association.
Project Details
Project type
Capability Research
Start Date
2004-04-16
End Date
2004-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Lipton AS, RW Heck, M Hernick, CA Fierke, and PD Ellis. 2008. "Residue Ionization in LpxC Directly Observed by 67Zn NMR Spectroscopy." Journal of the American Chemical Society 130(38):12671-12679.
"NMR resonance assignments of the human high mobility group protein HMGA1." Journal of Biomolecular NMR 38(2):185. Proposal ID: 7794, 7794a ERICA Product ID: 221558 Buchko GW, S Ni, NM Lourette, RC Reeves, and MA Kennedy. 2007.
"NMR resonance assignments of the human high mobility group protein HMGA1." Proposal ID: 7794, 7794a ERICA Product ID: 221558 Buchko GW, S Ni, NM Lourette, RC Reeves, and MA Kennedy. 2007.