Inhibition of DNA binding by human estrogen-related receptor 2 and estrogen receptor alpha with minor groove binding polyamides

Human estrogen-related receptor 2 (hERR2, ESRRB, ERRbeta, NR3B2) belongs to a class of nuclear receptors that bind DNA through sequence-specific interactions with a 5'-AGGTCA-3' estrogen response element (ERE) half-site in the major groove and an upstream 5'-TNA-3' site in the minor groove. This minor groove interaction is mediated by a C-terminal extension (CTE) of the DNA binding domain and is unique to the estrogen-related receptors. We have used synthetic pyrrole-imidazole polyamides, which bind specific sequences in the minor groove, to demonstrate that DNA binding by hERR2 is sensitive to the presence of polyamides in both the upstream minor groove CTE site and the minor groove of the ERE half-site. Thus, polyamides can inhibit hERR2 by two mechanisms, by direct steric blockage of minor groove DNA contacts mediated by the CTE and by changing the helical geometry of DNA such that major groove interactions are weakened. To confirm the generality of the latter approach, we show that the dimeric human estrogen receptor alpha (hERalpha, ESR1, NR3A1), which binds in the major groove of the ERE, can be inhibited by a polyamide bound in the opposing minor groove of the ERE. These results highlight two mechanisms for inhibition of protein-DNA interactions and extend the repertoire of DNA recognition motifs that can be inhibited by polyamides. These molecules may thus be useful for controlling expression of hERR2- or hERalpha-responsive genes.     

The phenotype and genotype of rheumatoid arthritis in the Democratic Republic of Congo

Introduction

Little is known about rheumatoid arthritis in the black, particularly in Congolese, populations. Our objective was to describe the phenotype and genotype of rheumatoid arthritis (RA) in Congolese.

Methods

All consecutive rheumatoid arthritis (RA) patients attending Kinshasa University Hospital in a three-year time period were included. Demographics, clinical features and tobacco consumption were noted. Disease Activity Score (DAS)-28 based on the erythrocyte sedimentation rate (ESR), Health Assessment Questionnaire (HAQ), anti-citrullinated peptide antibodies (CCP) antibodies and rheumatoid factor (RF) were determined. Radiographs were scored according to Sharp-van der Heijde. On a subset of patients and controls HLA-DRB1 typing was performed.

Results

A total of 114 females and 14 males aged 51.2 ± 14.9 were included. Mean duration of symptoms was four years. Moderate tobacco consumption was reported in a minority of patients. DAS-28 at first visit was >5.1 and HAQ ≥0.5 in all patients. X-rays showed joint erosions and/or joint space narrowing, mostly of a moderate grade in 55.8% of patients. Anti-CCP and/or RF were present in 48.6% of patients with available data (n = 72) and in 3.0% of controls (n = 67). Radiographic changes and nodules were more frequent in RF or anti-CCP positive patients. One copy of the shared epitope was found in 13 patients (35.1%) and 3 controls (12.5%). Two copies were found in one patient (2.7%) and in one control (4.2%).

Conclusion

Congolese patients with RA consult long after disease onset. Despite this delay, the majority presents without major damage and is RF, anti-CCP and SE negative. We put forward the hypothesis that besides different environmental factors there is probably also a particular genetic risk profile in Congolese patients, different from the HLA-DRB1 shared epitope.     

Solid-phase synthesis of DNA binding polyamides on oxime resin

Control of the energetics and specificity of DNA binding polyamides is necessary for inhibition of protein-DNA complex formation and gene regulation studies. Typically, solid-phase methods using Boc monomers for synthesis have depended on Boc-beta-Ala-PAM resin which affords a beta-alanine-Dp tail at the C-terminus, after cleavage with N,N-dimethylaminopropylamine (Dp). To address the energetic consequences of this tail for DNA minor groove binding, we describe an alternative solid phase method employing the Kaiser oxime resin which allows the synthesis of polyamides with incrementally shortened C-terminal tails. Polyamides without Dp and having methyl amide tails rather than beta-alanine show similar affinity relative to the standard beta-Dp tail. The truncated tail diminishes the A,T base pair energetic preference of the beta-Dp tail which will allow a greater variety of DNA sequences to be targeted by hairpin polyamides.     

DNA sequence selectivity of hairpin polyamide turn units

A class of hairpin polyamides linked by 3,4-diaminobutyric acid, resulting in a β-amine residue at the turn unit, showed improved binding affinities relative to their α-amino-γ-turn analogs for particular sequences. We incorporated β-amino-γ-turns in six-ring polyamides and determined whether there are any sequence preferences under the turn unit by quantitative footprinting titrations. Although there was an energetic penalty for G·C and C·G base pairs, we found little preference for T·A over A·T at the β-amino-γ-turn position. Fluorine and hydroxyl substituted α-amino-γ-turns were synthesized for comparison. Their binding affinities and specificities in the context of six-ring polyamides demonstrated overall diminished affinity and no additional specificity at the turn position. We anticipate that this study will be a baseline for further investigation of the turn subunit as a recognition element for the DNA minor groove.