Egr-1 is an inducible transcription factor that recognizes 9-bp target DNA sites via three zinc finger domains and activates genes in response to cellular stimuli such as synaptic signals and vascular stresses. Using spectroscopic and computational approaches, we have studied structural, dynamic, and kinetic aspects of the DNAscanning process in which Egr-1 is nonspecifically bound to DNA and perpetually changes its location on DNA. Our NMR data indicate that Egr-1 undergoes highly dynamic domain motions when scanning DNA. In particular, the zinc finger 1 (ZF1) of Egr-1 in the nonspecific complex is mainly dissociated from DNA and undergoes collective motions on a nanosecond timescale, whereas zinc fingers 2 and 3 (ZF2 and ZF3, respectively) are bound to DNA. This was totally unexpected because the previous crystallographic studies of the specific complex indicated that all of Egr-1's three zinc fingers are equally involved in binding to a target DNA site. Mutations that are expected to enhance ZF1's interactions with DNA and with ZF2 were found to reduce ZF1's domain motions in the nonspecific complex suggesting that these interactions dictate the dynamic behavior of ZF1. By experiment and computation, we have also investigated kinetics of Egr-1's translocation between two nonspecific DNA duplexes. Our data on the wild type and mutant proteins suggest that the domain dynamics facilitate Egr-1's intersegment transfer that involves transient bridging of two DNA sites. These results shed light on asymmetrical roles of the zinc finger domains for Egr-1 to scan DNA efficiently in the nucleus.NMR spectroscopy | target search process | interdomain dynamics | protein-DNA interactions | simulation I n cellular responses to various stimuli such as signals and stresses, gene regulation by transcription factors is of fundamental importance. Egr-1 (also known as Zif268) is an inducible transcription factor with crucial roles particularly in the brain and cardiovascular systems in mammals. In the brain, Egr-1 is induced by synaptic signals in an activity-dependent manner and activates genes for long-term memory formation and consolidation (1, 2). In the cardiovascular system, Egr-1 is a stress-inducible transcription factor that activates the genes for initiating defense responses against vascular stress and injury (3, 4). Given the short lifetime of induced Egr-1 (typically ∼2 h) (3), rapid gene activation by Egr-1 is important in these biological processes that require an immediate response to the stimuli.The induced Egr-1 protein has to initiate its role by searching for its target DNA sites among billions of DNA base pairs in the nucleus. In the DNA scanning process, transcription factors need to discriminate their target sites from nonspecific sites based on relatively minor differences in DNA structure and sequence. Crystallographic studies demonstrated that Egr-1 recognizes its 9-bp target sequence, GCGTGGGCG, as a monomer via zinc finger domains 1, 2, and 3 (hereafter referred to as ZF1, ZF2, and ZF3) that contact 3 ...

Background: Redox of extracellular HMGB1 protein plays an important role in inflammation. Results: The half-life of all-thiol HMGB1 was ϳ17 min in serum and saliva and significantly longer in cancer cell culture medium and was modulated by exogenous ligands (e.g. heparin). Conclusion:The extracellular environment dictates HMGB1 oxidation kinetics. Significance: Our approach permits investigating protein oxidation in situ.

Characterization of intrinsically disordered proteins (IDPs) has grown tremendously over the past two decades. NMR-based structural characterization has been widely embraced by the IDP community, largely because this technique is amenable to highly flexible biomolecules. Particularly, carbon-detect nuclear magnetic resonance (NMR) experiments provide a straight forward and expedient method for completing backbone assignments, thus providing the framework to study the structural and dynamic properties of IDPs. However, these experiments remain unfamiliar to most NMR spectroscopists, thus limiting the breadth of their application. In an effort to remove barriers that may prevent the application of carbon-detected bio-NMR where it has the potential to benefit investigators, here we describe the experimental requirements to collect a robust set of carbon-detected NMR data for complete backbone assignment of IDPs. Specifically, we advocate the use of threedimensional experiments that exploit magnetization transfer pathways initiated on the aliphatic protons, which produces increased sensitivity and provides a suitable method for IDPs that are only soluble in basic pH conditions (>7.5). The applicability of this strategy to systems featuring a high degree of proline content will also be discussed.

The High Mobility Group B1 (HMGB1) protein plays important roles in both intracellular (reductive) and extracellular (oxidative) environments. We have carried out quantitative investigations of the redox chemistry involving Cys22 and Cys44 of the HMGB1 A-domain, which form an intramolecular disulfide bond. Using NMR spectroscopy, we analyzed the realtime kinetics of the redox reactions for the A-domain in glutathione and thioredoxin systems, and also determined the standard redox potential. Thermodynamic experiments showed that the Cys22-Cys44 disulfide bond stabilizes the folded state of the protein. These data suggest that the oxidized HMGB1 may accumulate even in cells under oxidative stress. Structured summary:MINT-6795963: txn (uniprotkb:P10599) and HMGB1 (uniprotkb:P09429) bind (MI:0408) by nuclear magnetic resonance (MI:0077)

There is an extraordinary need to describe the structures of intrinsically disordered proteins (IDPs) due to their role in various biological processes involved in signaling and transcription. However, general study of IDPs by NMR spectroscopy is limited by the poor 1H-amide chemical shift dispersion typically observed in their spectra. Recently, 13C direct-detected NMR spectroscopy has been recognized as enabling broad structural study of IDPs. Most notably, multi-dimensional experiments based on the 15N,13C-CON spectrum make complete chemical shift assignment feasible. Here we document a collection of NMR based tools that efficiently lead to chemical shift assignment of IDPs, motivated by a case study of the C-terminal disordered region from the human pancreatic transcription factor Pdx1. Our strategy builds on the combination of two 3D experiments, (HN-flip)N(CA)CON and 3D (HN-flip)N(CA)NCO, that enable daisy-chain connections to be built along the IDP backbone, facilitated by acquisition of amino-acid specific 15N,13C-CON detected experiments. Assignments are completed through carbon-detected, TOCSY based side chain chemical shift measurement. Conducting our study required producing valuable modifications to many previously published pulse sequences, motivating us to announce the creation of a database of our pulse programs, which we make freely available through the web.