Different DNA contact schemes are used by two winged helix proteins to recognize a DNA binding sequence

The hepatocyte nuclear factor 3 (HNF-3)/fork head (fkh) family contains a large number of transcription factors which recognize divergent DNA sequences via a winged-helix binding motif. In this report we present studies on the DNA binding properties of winged-helix HNF-3/fkh homologues 1 (HFH-1) and 2 (HFH-2) which recognize a shared DNA binding site with different affinities. To explore how HFH-1 and HFH-2 proteins recognize this DNA binding sequence, the binding affinities of these two HFH proteins toward a series of DNA sites containing a single strand trimer loop insertion at different positions were studied. This insertion induces a bend of approximately 80 degrees in the DNA binding site (prebending). HFH-1 and HFH-2 were shown to recognize DNA sites prebent at many nucleotide positions on both strands of the DNA sequence. Both HFH-1 and HFH-2 were more sensitive to mismatch insertions on the sense strand of the DNA binding site, especially within the AAAATAAC sequence. Our data suggest that the recognition helix (helix 3) recognizes the AAAATAAC sequence and that the helix 3/DNA interaction results in bending of the DNA which narrows the major groove in the AAAATAAC sequence. Furthermore, the binding affinities of HFH-1 and HFH-2 toward DNA binding sites with base-pair reversion in the AAAATAAC sequence was also investigated. Different patterns of response from HFH-1 and HFH-2 to both prebent and base-pair reverted binding sites was observed. Our results demonstrate that even two highly conserved members of the winged-helix family may contact the same DNA sequence differently.

Susceptibility to beta-lactam antibiotics of Pseudomonas aeruginosa overproducing penicillin-binding protein 3

By using a broad-host-range vector, pUCP27, the Pseudomonas aeruginosa and Escherichia coli pbpB genes, which encode penicillin-binding protein 3 (PBP3), were separately overexpressed in a P. aeruginosa strain, PAO4089, that is deficient in producing chromosomal beta-lactamase. Susceptibility studies indicated that overproduction of the P. aeruginosa PBP3 in PAO4089 resulted in twofold-increased resistance to aztreonam, fourfold-increased resistance to cefepime and cefsulodin, and eightfold-increased resistance to ceftazidime, whereas overproduction of the P. aeruginosa PBP3 in PAO4089 did not affect susceptibility to PBP1-targeted cephaloridine or PBP2-targeted imipenem. Similar results were obtained with PAO4089 overproducing E. coli PBP3, with the exception that there was no influence on the MICs or minimal bactericidal concentrations of cefsulodin and cefepime, which have very low affinities for E. coli PBP3. These data are consistent with the conclusion that PBP3 has to achieve a certain level of saturation, with beta-lactams targeted to this protein, to result in cell inhibition or death.

Proviral integrations at the Evi5 locus disrupt a novel 90 kDa protein with homology to the Tre2 oncogene and cell-cycle regulatory proteins

Evi5 is a common site of retroviral integration in T-cell lymphomas of AKXD mice. Mapping studies have localized Evi5 to a region approximately 18 kb upstream of another common viral integration site, Gfi1, on mouse chromosome 5 (Liao X, Jenkins NA and Copeland NG, (1995a). J. Virol., 69, 7132-7137). Gfi1 encodes a zinc finger transcription factor involved in interleukin-2 signaling. To determine if Evi5 encodes a gene separate from Gfi1 that might also be involved in T-cell disease, we have searched within the Evi5 locus for novel transcripts. A 6.0 kb transcript was identified in these studies that spans the Evi5 locus and is disrupted by viral integration at Evi5. This transcript is expressed in all embryonic and adult mouse tissues examined. While blast searches indicated that Evi5 is a novel gene, homologies were detected between Evi5 and a known oncogene, Tre2, as well as mammalian and yeast cell cycle regulatory proteins. Evi5 thus encodes a gene separate from Gfi1 that may also be involved in T-cell disease.

Identification of a penicillin-binding protein 3 homolog, PBP3x, in Pseudomonas aeruginosa: gene cloning and growth phase-dependent expression

A homolog of Pseudomonas aeruginosa penicillin-binding protein 3 (PBP3), named PBP3x in this study, was identified by using degenerate primers based on conserved amino acid motifs in the high-molecular-weight PBPs. Analysis of the translated sequence of the pbpC gene encoding this PBP3x revealed that 41 and 48% of its amino acids were identical to those of Escherichia coli and P. aeruginosa PBP3s, respectively. The downstream sequence of pbpC encoded convergently transcribed homologs of the E. coli soxR gene and the Mycobacterium bovis adh gene. The pbpC gene product was expressed from the T7 promoter in E. coli and was exported to the cytoplasmic membrane of E. coli cells and could bind [3H] penicillin. By using a broad-host-range vector, pUCP27, the pbpC gene was expressed in P. aeruginosa PAO4089. [3H]penicillin-binding competition assays indicated that the pbpC gene product had lower affinities for several PBP3-targeted beta-lactam antibiotics than P. aeruginosa PBP3 did, and overexpression of the pbpC gene product had no effect on the susceptibility to the PBP3-targeted antibiotics tested. By gene replacement, a PBP3x-defective interposon mutant (strain HC132) was obtained and confirmed by Southern blot analysis. Inactivation of PBP3x caused no changes in the cell morphology or growth rate of exponentially growing cells, suggesting that pbpC was not required for cell viability under normal laboratory growth conditions. However, the upstream sequence of pbpC contained a potential sigma(s) recognition site, and pbpC gene expression appeared to be growth rate regulated. [3H]penicillin-binding assays indicated that PBP3 was mainly produced during exponential growth whereas PBP3x was produced in the stationary phase of growth.

Isolation and characterization of the platelet-derived growth factor beta receptor promoter

The PDGFbeta r gene has been implicated in many physiological processes including development and wound healing. Aberrant expression of the receptor is seen in many pathological conditions such as atherosclerosis and inflammatory diseases. To study the mechanisms of PDGFbeta r regulation, we identified the regulatory regions of the gene. We have cloned and characterized the promoter region of the platelet-derived growth factor beta receptor (PDGFbeta r). We isolated a 4.5 Kb genomic fragment which confers PDGFbeta r tissue-specific promoter activity. This fragment can direct transcription of a luciferase reporter gene in a cell-specific manner which correlates well with the known pattern of expression of the PDGFbeta r. The specificity of this clone was demonstrated by its high activity in NIH 3T3 fibroblasts and lack of activity in N-MUNG epithelial cells, a pattern that parallels the expression of the endogenous PDGFbeta r. We have defined a 614 bp region encompassing the 5' untranslated region of the gene which includes the basal promoter region. We generated transgenic mice that carry the chloramphenicol acetyltransferase (CAT) reporter gene under the control of the 4.5 Kb promoter. The expression pattern of the reporter gene was compared to that of the endogenous PDGFbeta r gene. The promoter was able to direct reporter gene expression with the same temporal and spatial pattern as the endogenous PDGFbeta r. The most prominent expression was in condensing mesenchyme of developing blood vessels, bone and tissues adjacent to epithelium. We conclude that this clone contains the regulatory regions sufficient to direct expression of the PDGFbeta r. The further analysis of this promoter will help elucidate the transcriptional regulation of expression of the PDGFbeta r, and provide a useful tool for directing expression of heterologous genes.

Monocyte chemoattractant protein-1 is sufficient for the chemotaxis of monocytes and lymphocytes in transgenic mice but requires an additional stimulus for inflammatory activation

Monocyte chemoattractant protein-1 (MCP-1), a chemotactic cytokine, acts in vitro as a chemotactic and activating factor for multiple types of leukocytes. To determine the chemotactic and activating effects of MCP-1 in vivo, we constructed transgenic mice that express human MCP-1 in type II alveolar epithelial cells and secrete it into the bronchoalveolar space. We found that MCP-1 overexpression led to a marked increase in the numbers of both monocytes and lymphocytes that could be recovered by bronchoalveolar lavage. This accumulation of mononuclear leukocytes could be reversed by the administration of an MCP-1-blocking Ab. In spite of its chemotactic effect, MCP-1 expression did not cause the inflammatory activation of accumulated leukocytes. Lungs of MCP-1 transgenic mice also showed no morphologic evidence of inflammation. However, MCP-1 mice had an increased sensitivity to other inflammatory stimuli. MCP-1 mice treated with either i.p. LPS or i.v. yeast wall glucan developed consolidated pulmonary infiltrates consisting predominantly of macrophages. Nontransgenic mice developed no such infiltrates. These results demonstrate that MCP-1 is chemotactic for monocytes and lymphocytes in vivo and that MCP-1 expression alone does not cause inflammatory activation of cells, but leads to an enhanced inflammatory response upon treatment with other stimuli.

Monocyte chemoattractant protein-1 is sufficient for the chemotaxis of monocytes and lymphocytes in transgenic mice but requires an additional stimulus for inflammatory activation

Monocyte chemoattractant protein-1 (MCP-1), a chemotactic cytokine, acts in vitro as a chemotactic and activating factor for multiple types of leukocytes. To determine the chemotactic and activating effects of MCP-1 in vivo, we constructed transgenic mice that express human MCP-1 in type II alveolar epithelial cells and secrete it into the bronchoalveolar space. We found that MCP-1 overexpression led to a marked increase in the numbers of both monocytes and lymphocytes that could be recovered by bronchoalveolar lavage. This accumulation of mononuclear leukocytes could be reversed by the administration of an MCP-1-blocking Ab. In spite of its chemotactic effect, MCP-1 expression did not cause the inflammatory activation of accumulated leukocytes. Lungs of MCP-1 transgenic mice also showed no morphologic evidence of inflammation. However, MCP-1 mice had an increased sensitivity to other inflammatory stimuli. MCP-1 mice treated with either i.p. LPS or i.v. yeast wall glucan developed consolidated pulmonary infiltrates consisting predominantly of macrophages. Nontransgenic mice developed no such infiltrates. These results demonstrate that MCP-1 is chemotactic for monocytes and lymphocytes in vivo and that MCP-1 expression alone does not cause inflammatory activation of cells, but leads to an enhanced inflammatory response upon treatment with other stimuli.

Upregulation of Gfi-1, a gene involved in IL-2-independent growth of T cells, in a murine retrovirus-induced immunodeficiency syndrome

BACKGROUND

A prominent feature of retrovirus-induced immunodeficiency in mice (MAIDS) is early polyclonal activation of CD4+ T cells followed by the appearance of monoclonal lymphomas marked by clonal proviral integrations. These events appear to occur independent of interleukin-2 (IL-2), suggesting the activity of an alternative growth-promoting pathway. We studied the possible contributions to T cell expansion of a gene, Gfi-1, previously shown to confer IL-2 independence to rat T cell lymphomas.

MATERIALS, RESULTS, CONCLUSIONS

We studied 17 mice with MAIDS that had clonal populations of T cells. Proviral integrations at Gfi-1 were detected in two animals. These integrations were associated with enhanced transcription of Gfi-1. Unexpectedly, elevated levels of Gfi-1 transcripts were also observed in four T cell lymphomas without detectable integrations at this locus. This suggests that IL-2-independent T cell growth in MAIDS may be driven by transcriptional activation of Gfi-1 by proviral insertion or transactivation.

Effect of epidural block on the lag time of pulse oximeter response

Thirty-six healthy patients, ASA 1, aged 16-41 years, scheduled for elective plastic surgery were studied to determine if thoracocervical or lumbar epidural blocks affected the lag time of the pulse oximeter response. Patients were allocated to receive thoracocervical epidural block (n = 20) (group 1) (lignocaine 1%) or lumbar epidural block (n = 16) (group 2) (lignocaine 1.5%). Epidural block was performed with a 17-gauge Tuohy needle inserted in the midline between C7-T2 vertebrae in group 1 and between L1-S1 in group 2 and an epidural catheter was introduced. Arterial oxygen saturation (SpO2) was measured continuously using a Datex pulse oximeter. The lag time of the pulse oximeter response was measured while breathing oxygen (100%) after breath-holding. Values were obtained 10 min before and 5, 10, 15, 20, 30, and 40 min after epidural injection of a test dose. There was a progressive decrease in the lag time of the pulse oximeter response so that by 30 min after epidural injection the mean (SD) value had decreased from 29 (6.1) to 14 (3.4) in Group 1 and 41 (12.8) to 23 (7.9) s in group 2 (p < 0.01).

Study of the safe threshold of apneic period in children during anesthesia induction

STUDY OBJECTIVES

(1) To investigate changes in arterial oxygen saturation via pulse oximeter (SpO2) during apnea and after reinstitution of manual ventilation at SpO2 of 95% or 90% following rapid sequence induction of anesthesia in children after 2-minute preoxygenation; (2) to determine whether the setting of a safe threshold of apneic period to an SpO2 of 95% is appropriate in children during anesthetic induction; and (3) to evaluate the influences of age, body weight, and height on the time from the start of apnea to SpO2 of 95%.

DESIGN

A clinical study of random design and comparison among groups.

SETTING

Operating room of a plastic surgery hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College.

PATIENTS

152 infants and children, ASA physical status 1, aged 3 months to 12 years, scheduled for elective plastic surgery.

INTERVENTIONS

Patients were divided into three age groups: Group 1-infants 3 months to 1 year (n = 39); Group 2 children 1 to 3 years (n = 41); and Group 3-children 3 to 12 years (n = 72). Patients in each age group were randomly allocated again to Subgroups A and B. After a 2-minute preoxygenation, anesthesia was induced with thiopental 5 mg/kg, fentanyl 5 micrograms/kg and suxamethonium 1.5 mg/kg. Patients were manually ventilated when SpO2 decreased to 90% in Subgroups A and 95% in Subgroups B, respectively, during apnea.

MEASUREMENTS AND MAIN RESULTS

SpO2 was measured continuously with a Datex pulse oximeter applied to the right index finger. During apnea, the times for SpO2 to decrease to 09% (T99) and 95% (T99) in all children, and 90% (T90) in Subgroups A were recorded. The time for SpO2 to decrease from 95% to 90% (T95-90) in Subgroups A was also measured. After reinstitution of manual ventilation, the time when SpO2 continued to decrease (T1) and the time from the end of apnea to recovery of SpO2 baseline (T2) were determined. In addition, the lowest value of SpO2 after apnea was also recorded. The results showed that younger children were more susceptible than older children to the risk of hypoxemia during apnea. There were significant differences in T99, T95, T90, and T95-90 between the three age groups T1 and T2 were significantly longer in Group 3 than in Groups 1 and 2. There were significant differences in the lowest values of SpO2 following apnea among the three Subgroups A and between Subgroups A and B of each age group. During apnea, heart rate decreased gradually as SpO2 decreased, showing a significant decrease at SpO2 of 95%. Bradycardia was found in three children in Subgroups A. The apnea time to SpO2 of 95% correlated well with age, weight, and height by linear regression analysis.

CONCLUSIONS

The safe threshold of an apneic period setting to an SpO2 of 95% was appropriate in children during anesthesia induction. Despite the same duration of preoxygenation, younger children were more susceptible than elder ones to the risk of hypoxemia during apnea. The apnea time to SpO2 of 95% correlated with age, body weight, and height using linear regression analysis.

Molecular cloning and primary characterization of a single-chain antibody against human sarcoma-associated antigen p200

BACKGROUND

Monoclonal Antibody (MAb) 29-13 reacts with the human sarcoma-associated antigen (SAA) p200. We report here engineering and primary characterization of a single chain antibody (scFV2913).

MATERIALS AND METHODS

The scFV2913 recombinant gene, consisting of VH-linker-VK, was constructed with RT-PCR. This gene was cloned and expressed in E. coli. The renatured scFV2913 was used in the immunostaining study.

RESULTS

Consistent with its parent MAb 29-13, purified and renatured scFV2913 showed affinity and specificity to the SAA p200 according to the immuno-histochemical staining study of 99 specimens of human sarcomas and other tissues.

CONCLUSIONS

Due to its retained specificity and affinity, scFV2913 may be useful in immunodiagnosis and immunotherapy for sarcoma patients.

A comparative study of early postoperative hypoxemia in infants, children, and adults undergoing elective plastic surgery

To determine the influence of age on postoperative hypoxemia, we studied postoperative hypoxemia in 1152 patients, from infants to adults, ASA physical status I, undergoing elective plastic surgery. Subjects were divided into four groups on the basis of age: Group 1, infants aged 1 yr or less (n = 108); Group 2, children aged 1-3 yr (n = 240); Group 3, children aged 3-14 yr (n = 482); and Group 4, adults aged 14-58 yr (n = 322). Arterial oxygen saturation (Spo2) levels were recorded while patients were breathing room air in the postanesthesia recovery room shortly after arrival (0 min), and 5, 10, 15, 20, 30, 40, 50, 60, 120, and 180 min thereafter. Younger patients showed lower Spo2 levels and a higher incidence of hypoxemia during the early postoperative period. The incidences of hypoxemia (Spo2 = 86%-90%) and severe hypoxemia (Spo2 < or = 85%) in the recovery room were 30.6% and 16.7%, respectively, in Group 1, 20.0% and 10.0% in Group 2, 14.1% and 3.3% in Group 3, and 7.8% and 0.6% in Group 4. Hypoxemia occurred most commonly within 1 h after anesthesia, particularly during the first 40 min in infants and during the first 15 min in older children and adults. A significant correlation was found by linear regression analysis between low Spo2 levels on admission to the recovery room and children's age. Thereafter, Spo2 levels and the incidence of hypoxemia during the early postoperative period were related only to infants' recovery scores.

[Early postoperative hypoxemia in infants, children and adults undergoing elective plastic surgery]

Seven hundred ASA-class-1 patients undergoing elective plastic surgery were selected to study the effect of age on early postoperative hypoxemia with a pulse eximeter for continuous monitoring of arterial oxygen saturation (SpO2) in the postanesthesia recovery room. The patients were divided into four groups: group 1, 72 infants aged less than one year; group 2, 120 children aged from one to three years; group 3, 364 children aged over three years; and group 4, 144 adults aged from 18 to 58 years. The results showed that the younger the patients, the lower the SpO3 and the higher the incidence of hypoxemia in the early postoperative period. The incidences of early postoperative hypoxemia in the postanesthesia recovery room were 44.4% in group 1, 31.7% in group 2, 17.3% in group 3 and 8.3% in group 4. Early postoperative hypoxemia occurred most commonly within 40 min. in infants and within 15 min. in children aged over one year and adults.

Viability of transgenic mice expressing a platelet derived growth factor (PDGF) antagonist in plasma

BACKGROUND

Many studies have implicated PDGF in the development of diseases such as atherosclerosis. Previously, we showed in tissue culture that the soluble extracellular domain of the PDGF beta-receptor is capable of binding BB-PDGF with high affinity; therefore antagonizing the ability of BB-PDGF to stimulate cell growth.

METHODS

This work describes the efforts of expressing the soluble extracellular domain of the PDGF beta-receptor in transgenic mice. Driven by the albumin promoter, which is activated relatively late during embryonic development, the secreted form of the PDGF receptor protein was detected in plasma of the homozygous mice at a high concentration (approximately 60 micrograms/microL or approximately 545 nm).

RESULTS

Plasma from these transgenic mice was capable of blocking PDGF-induced receptor autophosphorylation in tissue culture. The mice appeared to be healthy, demonstrating that full PDGF beta-receptor function is not required for viability.

CONCLUSION

By expressing a high level of a soluble form of the extracellular domain of the PDGF receptor in transgenic mice, we have established a novel animal model that will allow us to gain insight into the role of the PDGF receptor in vascular diseases and other diseases involving PDGF stimulated cell proliferation.

Observation of early postoperative hypoxaemia in children undergoing elective plastic surgery

The incidence, severity and duration of early postoperative hypoxaemia were determined in 420 healthy infants and children undergoing elective plastic surgery. Mean value of preoperative SpO2 was 98.3 +/- 0.87%. However, it decreased significantly to 92.7 +/- 4.01% immediately following anaesthesia in the postanaesthesia recovery room (PAR) when children breathed room air. Then SpO2 gradually increased to 93.8 +/- 4.25% at 10 min, 95.4 +/- 3.14% at 30 min, 96.6 +/- 2.25% at 60 min, 96.9 +/- 1.69% at 120 min, and 97.4 +/- 1.55% at 180 min, respectively. The incidence of hypoxaemia and severe hypoxaemia, which were 14.8% and 6.2% respectively on arrival in the PAR, decreased significantly to 6.6% and 1.9%, 30 min later. The hypoxaemia occurred most commonly within 1 h, particularly the first 30 min following anaesthesia. The hypoxaemia was more common and more severe in children undergoing cleft palate repair than other kinds of plastic surgery. A significant correlation was found between low SpO2 levels on admission to the PAR and children's age, fentanyl doses, and the infants' recovery score.

Evi-5, a common site of retroviral integration in AKXD T-cell lymphomas, maps near Gfi-1 on mouse chromosome 5

We have identified a novel common site of retroviral integration, Evi-5, in AKXD T-cell lymphomas. All proviruses located at Evi-5 are clustered within a 7-kb genomic region and, where determined, are oriented in the same transcriptional direction. Interspecific backcross analysis localized Evi-5 to mouse chromosome 5, where it cosegregated with another common viral integration site, Gfi-1. Gfi-1 encodes a novel zinc finger transcription factor whose expression is thought to be important for interleukin-2 signaling. Physical mapping studies showed that Evi-5 is located approximately 18 kb upstream of Gfi-1, and Southern analysis showed that Gfi-1, like Evi-5, is a common integration site in AKXD T-cell tumors. With one exception, Evi-5 and Gfi-1 integrations were mutually exclusive. Ten of the tumors with Evi-5 or Gfi-1 integrations also harbored viral integrations at other common integration sites causally associated with T-cell disease. These results are consistent with the hypothesis that T-cell lymphomagenesis is a multistep disease and that viral integration at Evi-5 or Gfi-1 is causally associated with this disease process.

Cloning and characterization of the Pseudomonas aeruginosa pbpB gene encoding penicillin-binding protein 3

Clones containing the pbpB gene which encodes penicillin-binding protein (PBP) 3 of Pseudomonas aeruginosa were detected by hybridization by PCR amplification with primers based on the conserved sequences of high-molecular-weight PBPs. The translated amino acid sequence demonstrated 45% identity and had a total of 66% conserved amino acids relative to the Escherichia coli PBP3. The pbpB gene was located upstream of a gene homologous to the E. coli murE gene, which encodes uridine diphosphate-N-acetyl muramic acid-tripeptide synthetase. The overexpressed pbpB gene product reacted with 3H-penicillin G and had an apparent molecular weight of 60,000.

Children's development effecting blood oxygen desaturation following apnea

One hundred and fifty-six children aged from 4 months to 12 years undergoing elective plastic surgery were included in this study. All children were ASA physical status I, under normal development, ranging from 64 to 140 cm in body height and from 6.0 to 41.0 kg in body weight. Following 2-minute preoxygenation, the time when SpO2 dropped to 95% and 90% in apneic period had a close correlation with age, weight and height of children by means of linear and non-linear regression analysis. The smaller the children's weight, the higher the incidence of severe arterial desaturation after reinstitution of manual ventilation with 100% oxygen at SpO2 of 90%. It is suggested that younger children are more susceptible to hypoxemia than older ones during apnea and provided no problem existing other than oxygen delivery, an SpO2 of 95% might be the safe limitation of apnea in pediatric anesthesia induction.

Long-range motional restrictions in a multidomain zinc-finger protein from anisotropic tumbling

Structural characterization of biomolecules in solution by nuclear magnetic resonance (NMR) spectroscopy is based primarily on the use of interproton distances derived from homonuclear cross-relaxation experiments. Information about short time-scale dynamics, on the other hand, is obtained from relaxation rates of heteronuclear spin pairs such as 15N-1H. By combining the two types of data and utilizing the dependence of heteronuclear NMR relaxation rates on anisotropic diffusional rotational tumbling, it is possible to obtain structural information about long-range motional correlations between protein domains. This approach was applied to characterize the relative orientations and mobilities of the first three zinc-finger domains of the Xenopus transcription factor TFIIIA in aqueous solution. The data indicate that the motions of the individual zinc-finger domains are highly correlated on time scales shorter than 10 nanoseconds and that the average conformation of the three-finger polypeptide is elongated.

Physiological control of trophophase-idiophase separation in streptomycete cultures producing secondary metabolites

Cultures of Streptomyces coelicolor A3(2) produced actinorhodin in defined media with various carbon and nitrogen sources. Production occurred during biomass accumulation if assimilation of either the carbon or the nitrogen source limited the rate of growth. High growth rates tended to delay product synthesis until after biomass accumulation was complete, but fully biphasic fermentation profiles were achieved only with media supporting very rapid growth. The onset of actinorhodin production then coincided with a decline in the growth rate during transition of carbon-sufficient cultures to stationary phase. In cultures with maltose as a growth-limiting carbon source, depletion of phosphate increased the rate of actinorhodin biosynthesis, but did not alter the timing of its initiation. With defined media, the use of spores rather than vegetative mycelium as inocula reduced the overlap between trophophase and idiophase. The general guidelines for achieving biphasic production of actinorhodin in S. coelicolor A3(2) cultures could be used to obtain trophophase-idiophase separation in cultures of Streptomyces venezuelae producing chloramphenicol. However, the conditions needed to be modified to give optimized biphasic fermentations with individual strains. Under conditions favouring chloramphenicol production in a distinct idiophase, aromatic amine secondary metabolites in the same cultures of S. venezuelae were produced in a pattern that overlapped the trophophase, suggesting that conditions need to be tailored also to meet differences in the regulation of secondary metabolites.

Relative contributions of the zinc fingers of transcription factor IIIA to the energetics of DNA binding

We have expressed and purified a series of recombinant zinc finger polypeptides derived from the cDNA for the Xenopus 5 S gene-specific transcription factor TFIIIA. Dissociation constants for the interaction of each of the truncated polypeptides with the 5 S gene promoter have been measured using gel mobility shift assays. DNase I footprinting and proteolysis experiments provide additional insights into the interactions of individual fingers within complexes of the truncated proteins. These results are discussed in terms of recently proposed models for the TFIIIA-DNA interaction. The effects of mutations in two of the strongly binding proteins, zf1-3 and zf1-7, on DNA binding affinity have been investigated. Mutations have been made both in putative DNA-contact residues and in the linker regions between zinc fingers. The observed decreases in binding affinity cannot be explained simply in terms of loss of protein-DNA contacts. Our results support a model in which DNA binding is accomplished through sets of interacting zinc fingers that make different energetic contributions to the overall binding of the protein and different contacts with the DNA.

The function of KGF in morphogenesis of epithelium and reepithelialization of wounds

The function of keratinocyte growth factor (KGF) in normal and wounded skin was assessed by expression of a dominant-negative KGF receptor transgene in basal keratinocytes. The skin of transgenic mice was characterized by epidermal atrophy, abnormalities in the hair follicles, and dermal hyperthickening. Upon skin injury, inhibition of KGF receptor signaling reduced the proliferation rate of epidermal keratinocytes at the wound edge, resulting in substantially delayed reepithelialization of the wound.

Targeted expression of a dominant negative FGF receptor blocks branching morphogenesis and epithelial differentiation of the mouse lung

Mouse lung development begins when two lung buds sprout from the epithelium of the embryonic gut. Patterning of the airways is then accomplished by the outgrowth and repetitive branching of the two lung buds, a process called branching morphogenesis. One of the four fibroblast growth factor (FGF) receptor genes, FGFR2, is expressed in the epithelium of a number of embryonic organs including the lung buds. To block the function of FGFR2 during branching morphogenesis of the lung without affecting its function in other embryonic tissues, the human surfactant protein C promoter was used to target expression of a dominant negative FGFR2 exclusively to lung bud epithelium in transgenic mice. Newborn mice expressing the transgene were completely normal except that instead of normally developed lungs they had two undifferentiated epithelial tubes that extended from the bifurcation of the trachea down to the diaphragm, a defect that resulted in perinatal death. Thus, the dominant negative FGF receptor completely blocked airway branching and epithelial differentiation, without prohibiting outgrowth, establishing a specific role for FGFs in branching morphogenesis of the mammalian lung.

1H, 15N and 13C resonance assignments for the first three zinc fingers of transcription factor IIIA

The first three zinc fingers (ZF1-3) of transcription factor IIIA (TFIIIA) from Xenopus have been shown to contribute the majority of the binding energy to the intact TFIIIA-DNA interaction [Liao et al. (1992) J. Mol. Biol., 223, 857-871]. We have expressed a 92-amino acid polypeptide containing the three N-terminal zinc fingers of TFIIIA. This three-fingered polypeptide has been isotopically labeled with 15N and 13C in E. coli and purified to homogeneity. Assignment of backbone 1H, 15N, aliphatic 1H and 13C and aromatic 1H and 13C resonances of delta NZF1-3 has been obtained using a combination of single-, double- and triple-resonance multidimensional NMR experiments. The secondary structures for each finger have been determined from NOE connectivities, 3JNH alpha values and chemical shifts. The results show that each finger folds into a canonical beta-sheet-helix zinc finger structural motif, while the linkers adopt an extended structure. The helix between the two histidine ligands in ZF3 is distorted by zinc coordination, to accommodate the presence of four intervening amino acids instead of three as in ZF1 and ZF2.

Targeted expression of a dominant-negative FGF receptor mutant in the epidermis of transgenic mice reveals a role of FGF in keratinocyte organization and differentiation

In this study we used a dominant-negative FGF receptor mutant to block FGF function in a specific tissue of transgenic mice. The mutant receptor, which is known to block signal transduction in cells when co-expressed with wild-type receptors, was targeted to suprabasal keratinocytes using a keratin 10 promoter. The transgene was expressed specifically in the skin and highest expression levels were found in the tail. Expression of the mutant receptor disrupted the organization of epidermal keratinocytes, induced epidermal hyperthickening and resulted in an aberrant expression of keratin 6. This suggests that FGF is essential for the morphogenesis of suprabasal keratinocytes and for the establishment of the normal program of keratinocyte differentiation. Our study demonstrates that dominant-negative growth factor receptors can be used to block selectively the action of a growth factor in specific tissues of transgenic mice.

Functional interchangeability of the structurally similar tetranucleotide loops GAAA and UUCG in fission yeast signal recognition particle RNA

Signal recognition particle (SRP) RNA exhibits significant primary sequence conservation only in domain IV, a bulged hairpin capped by a GNRA (N, any nucleotide; R, purine) tetranucleotide loop except in plant homologs. Tetraloops conforming to this sequence or to the consensus UNCG enhance the stability of synthetic RNA hairpins and have strikingly similar three-dimensional structures. To determine the biological relevance of this similarity, as well as to assess the relative contributions of sequence and structure to the function of the domain IV tetraloop, we replaced the GAAA sequence in fission yeast SRP RNA with UUCG. Haploid strains harboring this substitution are viable, providing experimental evidence for the functional equivalence of the two tetraloops. We next tested the two sequences found in plant SRP RNAs at this location for function in the context of the Schizosaccharomyces pombe RNA. While substitution of CUUC does not allow growth, a viable strain results from replacing GAAA with UUUC. Although the viable tetraloop substitution mutants exhibit wild-type growth under normal conditions, all three express conditional defects. To determine whether this might be a consequence of structural perturbations, we performed enzymatic probing. The results indicate that RNAs containing tetraloop substitutions exhibit subtle differences from the wild type not only in the tetraloop itself, but also in the 3-base pair adjoining stem. To directly assess the importance of the latter structure, we disrupted it partially or completely and made the compensatory mutations to restore the helix. Surprisingly, mutant RNAs with as little as one Watson-Crick base pair can support growth.

Molecular basis for specific recognition of both RNA and DNA by a zinc finger protein

Transcription factor IIIA (TFIIIA) from Xenopus oocytes binds both the internal control region of the 5S ribosomal RNA genes and the 5S RNA transcript itself. The nucleic acid binding domain of TFIIIA contains nine tandemly repeated zinc finger motifs. A series of precisely truncated forms of this protein have been constructed and assayed for 5S RNA and DNA binding. Different sets of zinc fingers were found to be responsible for high affinity interactions with RNA and with DNA. These results explain how a single protein can exhibit equal affinities for these two very different nucleic acids.

Identification of RNA sequences and structural elements required for assembly of fission yeast SRP54 protein with signal recognition particle RNA

Signal recognition particle (SRP) is a ribonucleoprotein composed of six polypeptides and a single RNA molecule. SRP RNA can be divided into four structural domains, the last of which is the most highly conserved and, in Schizosaccharomyces pombe, is the primary location to which deleterious mutations map. The ability of mammalian SRP54 protein (SRP54p) to bind Escherichia coli 4.5S RNA, a homolog of SRP RNA which contains only domain IV, suggested that SRP54p might interact directly with this region. To determine whether domain IV is critical for SRP54p binding in fission yeast cells, we used a native immunoprecipitation-RNA sequencing assay to test 13 mutant SRP RNAs for the ability to associate with the protein in vivo. The G156A mutation, which alters the 5' residue of the noncanonical first base pair of the domain IV terminal helix and confers a mild conditional growth defect, reduces assembly of the RNA with SRP54p. Mutating either of the two evolutionarily invariant residues in the bulged region 5' to G156 is more deleterious to growth and virtually abolishes SRP54p binding. We conclude that the conservation of nucleotides 154 to 156 is likely to be a consequence of their role as a sequence-specific recognition element for the SRP54 protein. We also tested a series of mutants with nucleotide substitutions in the conserved tetranucleotide loop and adjoining stem of domain IV. Although tetraloop mutations are deleterious to growth, they have little effect on SRP54p binding. Mutations which disrupt the base pair flanking the tetraloop result in conditional growth defects and significantly reduce association with SRP54p. Disruption of the other two base pairs in the short stem adjacent to the tetranucleotide loop has similar but less dramatic effects on SRP54p binding. These data provide the first evidence that both sequence-specific contacts and the structural integrity of domain IV of SRP RNA are important for assembly with SRP54p.

RTG1 and RTG2: two yeast genes required for a novel path of communication from mitochondria to the nucleus

The expression of some nuclear genes is sensitive to the functional state of mitochondria, a process we term retrograde regulation. Here we show that retrograde regulation of the yeast CIT2 gene encoding peroxisomal citrate synthase depends on a new class of upstream activation site element (UASr) and two previously unidentified genes, RTG1 and RTG2. RTG1 encodes a protein of 177 amino acids with similarity to basic helix-loop-helix transcription factors that likely functions at the CIT2 UASr. RTG2 encodes a protein of 394 amino acids of unknown function. Cells containing null alleles of RTG1 and RTG2 are viable and respiratory competent. However, they are auxotrophic for glutamic or aspartic acid and cannot use acetate as a sole carbon source, suggesting that both the tricarboxylic acid and glyoxylate cycles are compromised. Thus, RTG1 and RTG2 are pivotal genes in controlling interorganelle communication between mitochondria, peroxisomes, and the nucleus.

Definition of the binding sites of individual zinc fingers in the transcription factor IIIA-5S RNA gene complex

A series of polypeptides containing increasing numbers of zinc fingers of Xenopus transcription factor IIIA has been generated and binding to the 5S RNA gene internal control region has been studied in order to elucidate the mode of interaction of the individual fingers with DNA. By using a combination of DNase I footprinting, methylation interference, and differential binding to mixtures of DNA fragments differing in length by single base pairs, the binding sites for individual fingers have been defined. These results have led to a model for the interaction of transcription factor IIIA with the internal control region in which fingers 1-3 bind in the major groove of the promoter C block, fingers 7-9 bind in the major groove of the A block, and finger 5 binds in the major groove of the intermediate element. Fingers 4 and 6 each bind across the minor groove, spanning these promoter elements.

Random mutagenesis of Schizosaccharomyces pombe SRP RNA: lethal and conditional lesions cluster in presumptive protein binding sites

Signal recognition particle (SRP), a ribonucleoprotein composed of six polypeptides and one RNA subunit, serves as an adaptor between the cytoplasmic protein synthetic machinery and the translocation apparatus of the endoplasmic reticulum. To begin constructing a functional map of the 7SL RNA component of SRP, we extensively mutagenized the Schizosaccharomyces pombe SRP7 gene. Phenotypes are reported for fifty-two mutant alleles derived from random point mutagenesis, seven alleles created by site-directed mutagenesis to introduce restriction sites into the SRP7 gene, nine alleles designed to pinpoint conditional lesions, and three alleles with extra nucleotides inserted at position 84. Our data indicate that virtually all single nucleotide changes as well as many multiple substitutions in this highly structured RNA are phenotypically silent. Six lethal alleles and eleven which result in sensitivity to the combination of high temperature and elevated osmotic strength were identified. These mutations cluster in conserved regions which, in the mammalian RNA, are protected from nucleolytic agents by SRP proteins. The effects of mutations in the presumptive binding site for a fission yeast SRP 9/14 homolog indicate that both the identity of a conserved residue and the secondary structure within which it is embedded are functionally important. The phenotypes of mutations in Domain IV suggest particular residues as base-specific contacts for the fission yeast SRP54 protein. A single allele which confers temperature-sensitivity in the absence of osmotic perturbants was identified in this study; the growth properties of the mutant strain suggest that the encoded RNA is somewhat defective even at the permissive temperature, and is most likely unable to correctly assemble with SRP proteins at the nonpermissive temperature.

[Studies and comparisons on chemical components of essential oils from Clematis hexapetala Pall. and Inula nervosa Wall]

Chemical components of the essential oils from clematis hexapetala and Inula nervosa were analyzed by using GC-MS-DS. The result shows that the major components of the essential oil from Inula nervosa are thymol and thymol isobutyrate, while the major components of the essential oil from Clematis hexapetala are palmitic acid and 3-hydroxy-4-methoxyl benzaldehyde.

[Preliminary report of efficacy of diabetic polyneuropathy treated with large dose inositol]

Ten diabetics with polyneuropathy were studied by taking 6g inositol tablets (each tablet contains 0.25g inositol) per day for three months. The results showed that large dose inositol could reduce the severity of clinical symptoms, but there was no improvement of the nerve conduction velocity. The possible mechanism of these changes was discussed. According to the clinical observation of the therapeutic effect in those 10 cases, the authors would deem that large dose inositol is an effective drug for diabetic polyneuropathy, and it is worthy of further clinical trial, but other sensitive indicators should be used to evaluate the efficacy of this drug.

Identification of an essential Schizosaccharomyces pombe RNA homologous to the 7SL component of signal recognition particle

We have cloned the gene encoding a novel small cytoplasmic RNA from the fission yeast Schizosaccharomyces pombe. Four lines of evidence support the idea that this RNA is a homolog of the 7SL RNA component of mammalian signal recognition particle (SRP), which targets presecretory proteins to the endoplasmic reticulum membrane. First, it shares limited but significant primary sequence homology with previously identified 7SL RNAs and can be folded into a similar secondary structure. Second, it possesses the 5' triphosphate characteristic of unprocessed RNA polymerase III transcripts, and moreover, it is the only fission yeast RNA in this size range with such a terminus. Third, its behavior in cell fractionation experiments suggests that it is part of a small ribonucleoprotein which forms salt-labile contacts with larger structures. Fourth, the particle containing S. pombe 7SL RNA resembles mammalian SRP in both size (11S) and affinity for DEAE-Sepharose. Disruption of the single-copy gene, designated slr1+, reveals that the RNA is indispensable for growth in fission yeast. This result is not surprising, since secretion is an essential cellular process.