Compression stockings as an effective treatment for erythema nodosum: Case series.

Erythema nodosum (EN) is a septal panniculitis that is characterized clinically by tender, erythematous, subcutaneous nodules that are predominately localized on the pretibial lower legs. EN affects women more than men and can be idiopathic or secondary to another disease process such as infection or an immune response. Treatment options for erythema nodosum are suboptimal and often involve significant side effects or require a change in lifestyle. We investigated the effects of moderate 20 mmHg to 30 mmHg compression stockings as an alternative treatment method in two female patients with recurrent erythema nodosum. In both cases, the patients wore the compression stockings daily. At the follow-up visit, the EN lesions were no longer tender to the touch, and postinflammatory hyperpigmentation changes had started. Both patients had a lasting clinical resolution.

H-NS regulation of IraD and IraM antiadaptors for control of RpoS degradation.

RpoS, the master sigma factor during stationary phase and under a variety of stress conditions, is regulated at multiple levels, including regulated degradation. Degradation is dependent upon ClpXP and the RssB adaptor protein. H-NS, a nucleoid-associated protein, affects the regulated degradation of RpoS; in the absence of H-NS, RpoS is stable. The mechanisms involved in this regulation were not known. We have found that H-NS inhibits the expression of iraD and iraM, the genes coding for two antiadaptor proteins that stabilize RpoS when overexpressed. The regulation by H-NS of iraM is independent from the previously demonstrated regulation by the PhoP/PhoQ two-component system. Moreover, differences in the behavior of several hns alleles are explained by a role for StpA, an H-NS-like protein, in the regulation of RpoS stability. This finding parallels recent observations for a role of StpA in regulation of RpoS stability in Salmonella.

Small RNA regulators and the bacterial response to stress.

Recent studies have uncovered dozens of regulatory small RNAs in bacteria. A large number of these small RNAs act by pairing to their target mRNAs. The outcome of pairing can be either stimulation or inhibition of translation. Pairing in vivo frequently depends on the RNA-binding protein Hfq. Synthesis of these small RNAs is tightly regulated at the level of transcription; many of the well-studied stress response regulons have now been found to include a regulatory RNA. Expression of the small RNA can help the cell cope with environmental stress by redirecting cellular metabolism, exemplified by RyhB, a small RNA expressed upon iron starvation. Although small RNAs found in Escherichia coli can usually be identified by sequence comparison to closely related enterobacteria, other approaches are necessary to find the equivalent RNAs in other bacterial species. Nonetheless, it is becoming increasingly clear that many if not all bacteria encode significant numbers of these important regulators. Tracing their evolution through bacterial genomes remains a challenge.

The two pattern speeds of NGC 3359.

Using both observations and theoretical techniques, we show that the barred spiral galaxy NGC 3359 contains two pattern speeds. The faster pattern speed for the bar is obtained from isophotal analysis and stellar orbit theory. To explain the spiral arms and the observed velocity field of the disk, a slower pattern speed is required. Nonlinear resonance coupling is the supporting theory for the existence of two pattern speeds for the galaxy. The best match of our models with the observed data indicates a pattern speed for the bar of 39.17 km.sec(-1) approximately kpc(-1) and a value between 10 and 16 km.sec(-1).kpc(-1) for the spiral.

Temperature sensing by the dsrA promoter.

Synthesis of the small regulatory RNA DsrA is under temperature control. The minimal dsrA promoter of 36 bp contains sufficient information to ensure such regulation. In vivo, we have analyzed the critical elements responsible for the temperature control of dsrA by using a collection of chimeric promoters combining various elements of the dsrA promoter and the lacUV5 promoter, which does not respond to temperature. Our results favor an RNA polymerase-DNA interaction model instead of a trans-acting factor for temperature regulation. While all of the elements of the dsrA promoter contribute to temperature-sensitive expression, the sequence of the -10 box and the spacer region are the essential elements for the thermal response of the dsrA promoter. The proper context for these promoter elements, including at least one of the flanking elements, the -35 region or the start site region, is also required. Point mutations demonstrate that the sequence of the -10 box imposes constraints on the length and the sequence of the spacer and/or its AT richness, even at low temperature. These results show a complex interdependence of different regions in the promoter for temperature regulation.

Small non-coding RNAs, co-ordinators of adaptation processes in Escherichia coli: the RpoS paradigm.

Adaptation to the changing environment requires both the integration of external signals and the co-ordination of internal responses. Around 50 non-coding small RNAs (sRNAs) have been described in Escherichia coli; the levels of many of these vary with changing environmental conditions. This suggests that they play a role in cell adaptation. In this review, we use the regulation of RpoS (sigma38) translation as a paradigm of sRNA-mediated response to environmental conditions; rpoS is currently the only known gene regulated post-transcriptionally by at least three sRNAs. DsrA and RprA stimulate RpoS translation in response to low temperature and cell surface stress, respectively, whereas OxyS represses RpoS translation in response to oxidative shock. However, in addition to regulating RpoS translation, DsrA represses the translation of HNS (a global regulator of gene expression), whereas OxyS represses the translation of FhlA (a transcriptional activator), allowing the cell to co-ordinate different pathways involved in cell adaptation. Environmental cues affect the synthesis and stability of specific sRNAs, resulting in specific sRNA-dependent translational control.

Identification of novel small RNAs using comparative genomics and microarrays.

A burgeoning list of small RNAs with a variety of regulatory functions has been identified in both prokaryotic and eukaryotic cells. However, it remains difficult to identify small RNAs by sequence inspection. We used the high conservation of small RNAs among closely related bacterial species, as well as analysis of transcripts detected by high-density oligonucleotide probe arrays, to predict the presence of novel small RNA genes in the intergenic regions of the Escherichia coli genome. The existence of 23 distinct new RNA species was confirmed by Northern analysis. Of these, six are predicted to encode short ORFs, whereas 17 are likely to be novel functional small RNAs. We discovered that many of these small RNAs interact with the RNA-binding protein Hfq, pointing to a global role of the Hfq protein in facilitating small RNA function. The approaches used here should allow identification of small RNAs in other organisms.

Signal transduction cascade for regulation of RpoS: temperature regulation of DsrA.

Many environmental parameters modulate the amount of the RpoS sigma factor in Escherichia coli. Temperature control of RpoS depends on the untranslated RNA DsrA. DsrA activates RpoS translation by pairing with the leader of the mRNA. We find that temperature affects both the rate of transcription initiation of the dsrA gene and the stability of DsrA RNA. Both are increased at low temperature (25 degrees C) compared to 37 or 42 degrees C. The combination of these results is 25-fold-less DsrA at 37 degrees C and 30-fold less at 42 degrees C than at 25 degrees C. Using an adapted lacZ-based reporter system, we show that temperature control of transcription initiation of dsrA requires only the minimal promoter of 36 bp. Overall, transcription responses to temperature lead to a sixfold increase in DsrA synthesis at 25 degrees C over that at 42 degrees C. Furthermore, two activating regions and a site for LeuO negative regulation were identified in the dsrA promoter. The activating regions also activate transcription in vitro. DsrA decays with a half-life of 23 min at 25 degrees C and 4 min at 37 and 42 degrees C. These results demonstrate that the dsrA promoter and the stability of DsrA RNA are the thermometers for RpoS temperature sensing. Multiple inputs to DsrA accumulation allow sensitive modulation of changes in the synthesis of the downstream targets of DsrA such as RpoS.

High-grade T-cell lymphoma complicating B-cell chronic lymphocytic leukemia: an unusual manifestation of "Richter's syndrome".

Approximately 3% of patients with B-cell chronic lymphocytic leukemia (CLL) develop a high-grade large-cell lymphoma consistent with Richter's Syndrome. In most cases, these lymphomas are of B-cell origin and are believed to arise by clonal evolution from the CLL cells. We present a case of a patient with a 10-year history of B-CLL who developed an aggressive large-cell lymphoma, confirmed by immunophenotype to be of T-cell origin. We suggest that in patients with CLL, immunodysregulation can result in the proliferation of T cells, which may mutate and result in the development of a new malignant clone.

Regulation of RpoS by a novel small RNA: the characterization of RprA.

Translational regulation of the stationary phase sigma factor RpoS is mediated by the formation of a double-stranded RNA stem-loop structure in the upstream region of the rpoS messenger RNA, occluding the translation initiation site. The interaction of the rpoS mRNA with a small RNA, DsrA, disrupts the double-strand pairing and allows high levels of translation initiation. We screened a multicopy library of Escherichia coli DNA fragments for novel activators of RpoS translation when DsrA is absent. Clones carrying rprA (RpoS regulator RNA) increased the translation of RpoS. The rprA gene encodes a 106 nucleotide regulatory RNA. As with DsrA, RprA is predicted to form three stem-loops and is highly conserved in Salmonella and Klebsiella species. Thus, at least two small RNAs, DsrA and RprA, participate in the positive regulation of RpoS translation. Unlike DsrA, RprA does not have an extensive region of complementarity to the RpoS leader, leaving its mechanism of action unclear. RprA is non-essential. Mutations in the gene interfere with the induction of RpoS after osmotic shock when DsrA is absent, demonstrating a physiological role for RprA. The existence of two very different small RNA regulators of RpoS translation suggests that such additional regulatory RNAs are likely to exist, both for regulation of RpoS and for regulation of other important cellular components.

The RssB response regulator directly targets sigma(S) for degradation by ClpXP.

The sigma(S) subunit of Escherichia coli RNA polymerase regulates the expression of stationary phase and stress response genes. Control over sigma(S) activity is exercised in part by regulated degradation of sigma(S). In vivo, degradation requires the ClpXP protease together with RssB, a protein homologous to response regulator proteins. Using purified components, we reconstructed the degradation of sigma(S) in vitro and demonstrate a direct role for RssB in delivering sigma(S) to ClpXP. RssB greatly stimulates sigma(S) degradation by ClpXP. Acetyl phosphate, which phosphorylates RssB, is required. RssB participates in multiple rounds of sigma(S) degradation, demonstrating its catalytic role. RssB promotes sigma(S) degradation specifically; it does not affect degradation of other ClpXP substrates or other proteins not normally degraded by ClpXP. sigma(S) and RssB form a stable complex in the presence of acetyl phosphate, and together they form a ternary complex with ClpX that is stabilized by ATP[gamma-S]. Alone, neither sigma(S) nor RssB binds ClpX with high affinity. When ClpP is present, a larger sigma(S)--RssB--ClpXP complex forms. The complex degrades sigma(S) and releases RssB from ClpXP in an ATP-dependent reaction. Our results illuminate an important mechanism for regulated protein turnover in which a unique targeting protein, whose own activity is regulated through specific signaling pathways, catalyzes the delivery of a specific substrate to a specific protease.

Posttranslational quality control: folding, refolding, and degrading proteins.

Polypeptides emerging from the ribosome must fold into stable three-dimensional structures and maintain that structure throughout their functional lifetimes. Maintaining quality control over protein structure and function depends on molecular chaperones and proteases, both of which can recognize hydrophobic regions exposed on unfolded polypeptides. Molecular chaperones promote proper protein folding and prevent aggregation, and energy-dependent proteases eliminate irreversibly damaged proteins. The kinetics of partitioning between chaperones and proteases determines whether a protein will be destroyed before it folds properly. When both quality control options fail, damaged proteins accumulate as aggregates, a process associated with amyloid diseases.

Redundant in vivo proteolytic activities of Escherichia coli Lon and the ClpYQ (HslUV) protease.

The ClpYQ (HslUV) ATP-dependent protease of Escherichia coli consists of an ATPase subunit closely related to the Clp ATPases and a protease component related to those found in the eukaryotic proteasome. We found that this protease has a substrate specificity overlapping that of the Lon protease, another ATP-dependent protease in which a single subunit contains both the proteolytic active site and the ATPase. Lon is responsible for the degradation of the cell division inhibitor SulA; lon mutants are UV sensitive, due to the stabilization of SulA. lon mutants are also mucoid, due to the stabilization of another Lon substrate, the positive regulator of capsule transcription, RcsA. The overproduction of ClpYQ suppresses both of these phenotypes, and the suppression of UV sensitivity is accompanied by a restoration of the rapid degradation of SulA. Inactivation of the chromosomal copy of clpY or clpQ leads to further stabilization of SulA in a lon mutant but not in lon+ cells. While either lon, lon clpY, or lon clpQ mutants are UV sensitive at low temperatures, at elevated temperatures the lon mutant loses its UV sensitivity, while the double mutants do not. Therefore, the degradation of SulA by ClpYQ at elevated temperatures is sufficient to lead to UV resistance. Thus, a protease with a structure and an active site different from those of Lon is capable of recognizing and degrading two different Lon substrates and appears to act as a backup for Lon under certain conditions.

Substrate sequestration by a proteolytically inactive Lon mutant.

Lon protein of Escherichia coli is an ATP-dependent protease responsible for the rapid turnover of both abnormal and naturally unstable proteins, including SulA, a cell division inhibitor made after DNA damage, and RcsA, a positive regulator of transcription. Lon is a multimer of identical 94-kDa subunits, each containing a consensus ATPase motif and a serine active site. We found that overexpressing Lon, which is mutated for the serine active site (LonS679A) and is therefore devoid of proteolytic activity, unexpectedly led to complementation of the UV sensitivity and capsule overproduction of a lon deletion mutant. SulA was not degraded by LonS679A, but rather was completely protected by the Lon mutant from degradation by other cellular proteases. We interpret these results to mean that the mutant LonS679A binds but does not degrade Lon substrates, resulting in sequestration of the substrate proteins and interference with their activities, resulting in apparent complementation. Lon that carried a mutation in the consensus ATPase site, either with or without the active site serine, was no longer able to complement a Deltalon mutant. These in vivo results suggest that the pathway of degradation by Lon couples ATP-dependent unfolding with movement of the substrate into protected chambers within Lon, where it is held until degradation proceeds. In the absence of degradation the substrate remains sequestered. Comparison of our results with those from a number of other systems suggest that proteins related to the regulatory portions of energy-dependent proteases act as energy-dependent sequestration proteins.

Regulation by proteolysis: developmental switches.

The energy-dependent proteases originally defined in Escherichia coli have proven to have particularly important roles in bacterial developmental systems, including sporulation in Bacillus subtilis and cell cycle in Caulobacter. Degradation of key regulatory proteins participates, with regulation of synthesis and activity of the regulators, to ensure tight control and, where required, irreversible commitment of the cell to specific developmental pathways.

Peripheral T cell lymphoma in a patient with common variable immunodeficiency disease: case report and literature review.

This report documents the occurrence of a peripheral T cell lymphoma arising in the bone marrow and liver of a patient with common variable immunodeficiency disease. The T cell origin of this lymphoma was demonstrated by immunohistochemical phenotyping and gene rearrangement studies and was not associated with EBV infection of the lymphoma cells. The frequency and characteristics of lymphomas complicating CVID are reviewed.

DsrA RNA regulates translation of RpoS message by an anti-antisense mechanism, independent of its action as an antisilencer of transcription.

DsrA RNA regulates both transcription, by overcoming transcriptional silencing by the nucleoid-associated H-NS protein, and translation, by promoting efficient translation of the stress sigma factor, RpoS. These two activities of DsrA can be separated by mutation: the first of three stem-loops of the 85 nucleotide RNA is necessary for RpoS translation but not for anti-H-NS action, while the second stem-loop is essential for antisilencing and less critical for RpoS translation. The third stem-loop, which behaves as a transcription terminator, can be substituted by the trp transcription terminator without loss of either DsrA function. The sequence of the first stem-loop of DsrA is complementary with the upstream leader portion of rpoS messenger RNA, suggesting that pairing of DsrA with the rpoS message might be important for translational regulation. Mutations in the Rpos leader and compensating mutations in DsrA confirm that this predicted pairing is necessary for DsrA stimulation of RpoS translation. We propose that DsrA pairing stimulates RpoS translation by acting as an anti-antisense RNA, freeing the translation initiation region from the cis-acting antisense RNA and allowing increased translation.