Biomedical subjects

K Asano

Publications and source records attributed to K Asano.

At least 109 records · Page 6Linked to original sources

PubMed1999

Peri-operative changes in echocardiographic measurements and plasma atrial and brain natriuretic peptide concentrations in 3 dogs with patent ductus arteriosus.

Peri-operative changes in echocardiographic measurements and plasma levels of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were investigated for 1 month in 3 dogs with patent ductus arteriosus (PDA). Post-operative left ventricular end-diastolic dimention and fractional shortening decreased in all cases. Pre-operatively increased plasma ANP concentrations reduced dramatically after the operation. Peri-operative changes in plasma BNP levels had slightly S-shaped curves in all cases. These observations suggest that post-operative responsiveness of ANP and cardiac function are rapid in comparison with cardiac morphological changes, and BNP has a different pathophysiological significance from ANP in dogs with PDA.

Animals↗

PubMed1999

[Double cancer observed from bladder cancer].

BACKGROUND: In recent years, despite of the improvement of treatment results for cancer and long life, the occurrence of second primary cancer was increased. In this paper, we analyzed present condition of double cancer observed with bladder cancer in our hospital. METHOD: Last 21 years, we have treated 969 cases (828 male and 141 female) of primary bladder cancer. For those cases, we analyzed in term of frequency, involved organ, age, interval between two cancer occurrence, risk factor and prognosis of double cancer patients. RESULT: Of 969 cases with bladder cancer, 81 cases (8.36%) had double cancer involving 6 cases (0.61%) of triple cancer. In sex, 70 males (9.78%) and 11 females (7.80%) had double cancer. As involved organs, 25 cases (3.02%) had in prostate, 23 cases (2.37%) in stomach, 3 case (2.13%) in breast, 14 cases (1.44%) in colon and rectum. In diagnosis timing of complicated cancer from bladder cancer, 28 cases (34.6%) were diagnosed previously to bladder, 28 cases (34.6%) were simultaneously and 31 cases (38.3%) were secondary. An average interval of diagnosis of two cancer were 49 +/- 42.5 months. An average age of occurrence of second cancer was 70.3 +/- 8.8 years. Actual survival rate from diagnosis of bladder cancer were 90.8%, 68.6%, 53.3% and 30.3%, after 1, 3, 5 and 10 years, respectively. Ten cases were dead by bladder cancer, 21 cases by complicated cancer and 16 cases by another cause. CONCLUSION: The incidence of double cancer with bladder cancer were increased. Prostate cancer, colorectal cancer and breast cancer were gradually increased as complicated organs in Japan. The prognosis of double cancer patients with bladder cancer was poor than single bladder cancer patients.

Adult↗

PubMed1999

[Clinical studies on inverted papilloma of the urinary tract].

BACKGROUND: Inverted papilloma of the urinary tract is believed to be a benign neoplasm based on its histologic morphology and clinical behavior. In recent years, however, several investigators have warned against too optimistic an approach, emphasizing the possibility of malignant cellular transformation within the lesion, or its eventual association with other urothelial tumors such as transitional cell carcinoma or carcinoma in situ. We here report on 35 clinicopathologically diagnosed cases of inverted papilloma, and present the clinical significance attributed to these lesions in view of the current literature. PATIENTS AND METHODS: From 1976 to 1997, 35 cases of inverted papilloma of the urinary tract were treated at our hospital. This report presents the clinical features of these cases, the results of prognosis research, an investigation of the cases in which inverted papilloma and transitional cell carcinoma were found to co-exist, and a discussion of the recurrent cases of inverted papilloma found in previous literature. RESULTS: The patients ranged from 24 to 77 years of age, with a mean of 54 years, and included 4 women and 31 men. The most frequently occurring symptom was grosshematuria, and more than 90% of the 35 cases occurred in the bladder. In 2 of the 35 cases, transitional cell carcinoma coexisted with the inverted papilloma, at a different location in the bladder in one case and within the same neoplasm in the ureter in the other case. Clinical courses after treatment were followed in 29 of the 35 cases, with a follow-up period of from 8 months to 19 years (mean follow-up, 5 years and 4 months). Of these 29 cases, 2 showed recurrence, one at 16 and one at 30 months after the initial resection. Many previous reports show that the association of inverted papilloma and transitional cell carcinoma is stronger in the upper urinary tract and recurrence of inverted papilloma almost always happens with 2 years. CONCLUSION: This study suggests that some cases of urinary inverted papilloma show recurrence or malignant potential. Our results indicate that all cases of urinary inverted papilloma should be treated and followed as cases of low-grade transitional cell carcinomas. Consequently, all cases must be followed for two years or more after the initial operation.

Adult↗

PubMed1999

[Long-term endoscopic follow-up for peptic ulcer patients after eradication of H. pylori; comparison with the maintainance therapy by H2-blocker].

This study was aimed to clarify the endoscopic findings and the decline of serum IgG titer after successful eradication of H. pylori in long-term (from 2 to 7 years). Forty-six H. pylori-positive peptic ulcer (22 GU and 26 DU) cases were eradicated with antimicrobial therapy. Sixty-nine non-eradicated DU cases who received maintainance therapy with H2-blocker were control group. Biopsy urease test (BUT) and culturing was performed to diagnose the H. pylori infection. Anti-H. pylori IgG titer (EIA) were also measured in some cases, pre and 6, 12, 24 months after the eradication. In 3 cases, H. pylori were recrudescent and only in a case, DU recurred during 5 years after eradication. Meanwhile, in 55% of control cases, DU were recurred during same periods. In 62% of eradicated cases, serum IgG-antibody to H. pylori declined below the cut-off level during 2 years after eradication. It was certified that eradication therapy against H. pylori prevents ulcer recurrence for long time, and re-rise of serum IgG titer to H. pylori might predict a recrudescence of infection.

Adult↗

PubMed1999

Complementary DNA cloning, tissue distribution, and synthesis of canine brain natriuretic peptide.

OBJECTIVE: To determine complimentary DNA (cDNA) sequence and tissue distribution of canine brain natriuretic peptide (BNP), and to investigate whether synthesis of canine BNP increases in association with cardiovascular dysfunction. ANIMALS: 5 healthy adult mixed-breed dogs and 3 healthy adult Beagles. PROCEDURE: Total RNA was extracted from normal canine hearts and was used in a reverse transcription-polymerase chain reaction (RT-PCR) procedure to isolate canine BNP cDNA. Sequence of the isolated cDNA was analyzed. Gene expression of canine BNP in various tissues from 2 mixed-breed dogs was investigated, using RT-PCR and northern blot analyses. Moreover, messenger RNA (mRNA) expression of canine BNP, using northern blot analysis, was compared between grossly normal hearts from 3 Beagles and hearts from 3 mixed-breed dogs with acute myocardial infarction created by surgical ligation. RESULTS: The cDNA sequence and deduced amino acid residues of canine BNP precursor were 420 base pairs and 140 residues, respectively. Messenger RNA expression of canine BNP was detectable in the atria but not in the ventricles and the other tissues. Messenger RNA expression of canine BNP was, however, detectable in the infarcted portion of the ventricles. The amount of canine BNP mRNA in the infarcted ventricles was significantly increased, compared with that of noninfarcted ventricles. CONCLUSION: The cDNA sequence of canine BNP was determined. Expression of canine BNP mRNA was detected not only in the atria but also in infarcted ventricles. Synthesis of canine BNP increases in association with ischemic myocardial injury. Canine BNP may be used as an indicator of severity of ventricular myocardial injury.

Amino Acid Sequence↗

PubMed1999

[Epidemiological survey of ocular diseases in K Island, Amami Islands: prevalence of cataract and pterygium].

PURPOSE: An epidemiological survey of ocular disease was performed in a town of the Amami Islands in southwestern Japan. OBJECT AND METHODS: A total of 339 participants over 40 years joined the survey. Among the 339 participants, the lens findings of 602 eyes of 301 subjects were analyzed. RESULTS: The prevalence of lens opacification was 32.0, 54.0, 83.1, 96.9% and 100% among subjects in their 40, 50, 60, 70 s, and over 80 years. Lens opacification over grade II was 4.0, 12.7, 26.2, 60.0% and 83.3%. The cataract type most frequently seen was cortical (96.1%), followed by 48.5% with nuclear opacity and 14.7% with subcapsular type. A high prevalence was seen of pterygium at 25.4%. Although the prevalence of lens opacification was higher in the group with pterygium in their 70 s, no significant difference was noticed in persons in their 40, 50, 60 s, and over 80 years old between the pterygium and non-pterygium groups. CONCLUSIONS: Similarly to the results of a previous survey in Okinawa, Noto, and Hokkaido, the main type of lens opacification was cortical in Amami. The prevalence of nuclear opacification and pterygium was higher than in Noto and Hokkaido, and close to that seen in Okinawa.

Adult↗

PubMed1999

[Prognosis and organ preservation in oropharyngeal cancer treated with radiotherapy].

The records of 102 patients with squamous cell carcinoma of the oropharynx treated at National Sapporo Hospital with external and/or interstitial radiotherapy between 1978 and 1996 were reviewed to evaluate the treatment results, focusing on primary control and functional preservation. Ninety-five patients had been primarily treated with curative intent initially. Of these 95 patients, 4% were in stage I, 19% in stage II, 42% in stage III and 34% in stage IV. Twenty-one patients (22%) had been treated with multidisciplinary chemotherapy, and 19 patients (20%) had been boosted with brachytherapy mainly using Au-198 grains. The cause-specific survival rates at 5 and 10 years were 63% and 52%, respectively. The local control rates at 5 and 10 years were 70% and 51%, respectively. The most important factors affecting local control were the subsite of the primary tumor and N stage. Based on these findings, it is considered that radiotherapy combined with/without chemotherapy except for N3 and the posterior wall type is an effective method of achieving tumor control and preserving organ function, compared with other methods including surgical procedures.

Adult↗

PubMed1999

[Right phrenic nerve palsy in a patient with ventricular septal perforation after acute myocardial infarction].

A 77-year-old female had acute myocardial infarction and ventricular septal perforation (VSP). An operation was performed 14 days after VSP. During cardiopulmonary bypass, a patch was sutured in place on the left side of the defect under a mild hypothermia with topical cardiac cooling procedure. In the postoperative period, mechanical ventilation was continued with use of pulmonary monitor (CP-100, BICORE). When the patient was weaned of mechanical ventilation, work of breathing increased (WOBp: 1.67 J.l-1) without the change of SaO2, PaO2, PaCO2 and the respiratory state. After extubation, the chest X-ray showed elevated right diaphragmatic level and a diagnosis of unilateral diaphragmatic paralysis was made. Oral intake was started two days after extubation. SpO2 decreased after oral intake, and it was significantly improved by taking a left lateral position. The symptoms disappeared 47 days after the operation. It should be noticed that the rise of endoceliac pressure in the patient who had a unilateral phrenic nerve palsy, affected the SpO2.

Aged↗

PubMed1999

[Clinical investigation of pulmonary tuberculomas diagnosed by video-assisted thoracoscopic biopsy].

We investigated the clinical characteristics of pulmonary tuberculomas and discussed strategies for their diagnosis. We compared a group of patients with lesions that had been diagnosed by bronchoscopy (the BF group: 15 patients, 17 lesions) with a group whose lesions had been diagnosed by thoracoscopy (the VATS group: 19 patients, 20 lesions). The VATS group included patients with lesions that could not be diagnosed by bronchoscopy alone. The 2 groups did not differ significantly in terms of patient age, gender, lesion size, number of bronchoscopic examinations, or tuberculin test findings. In both groups, the lesions always existed just below the pleural surface and were mostly located in the upper lobes of the lungs. Lesion locations in the middle lobe and lingular segment were observed only in the BF group, whereas locations in the lower lobes were observed only in the VATS group. Tuberculomas in 2 BF group patients (11%) and 10 VATS group patients (50%) were diagnosed on the basis of histopathologic findings in the absence of bacteriological evidence. No postoperative complications were observed in the VATS group, and all patients in this group were discharged from the hospital within 1 week. No relapse of tuberculosis was observed in either group following anti-tuberculous therapy. Video-assisted thoracoscopic biopsy is a reliable and minimally invasive diagnostic procedure, and should be performed on any solitary pulmonary lesion that cannot be diagnosed by bronchoscopy. It is important that tuberculomas be quickly and accurately diagnosed not only in order to distinguish them from lung cancer, but also to treat the patient's tuberculosis at an early stage and prevent it from spreading.

Adult↗

PubMed1999

[A case of small cell carcinoma of the stomach with multiple liver and lung metastases successfully treated by combined chemotherapy with cisplatin and etoposide].

We experienced a case of small cell carcinoma of the stomach in which chemotherapy had been markedly effective. A 54-year-old man was admitted to our hospital complaining of hematemesis. Gastric endoscopy showed a type 2 tumor at the lesser curvature of the cardia of the remnant stomach. Total gastrectomy, splenectomy and D2 lymph node dissection were performed. Histopathologically, the tumor was diagnosed as a small cell carcinoma with findings of t 2 n 1 in stage II, and conclusive curability was A. A month after the operation, CT-scan revealed multiple liver and lung metastases, so the patient was treated by combined chemotherapy with cisplatin and etoposide called PVP for three courses every four weeks for small cell lung cancer, which resulted in remarkable reduction of metastases (96% in the liver and 81% in the lung). This result suggests that PVP chemotherapy is effective in the treatment of small cell carcinoma of the stomach as well as the lung.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1998

The essential Gcd10p-Gcd14p nuclear complex is required for 1-methyladenosine modification and maturation of initiator methionyl-tRNA.

Gcd10p and Gcd14p are essential proteins required for the initiation of protein synthesis and translational repression of GCN4 mRNA. The phenotypes of gcd10 mutants were suppressed by high-copy-number IMT genes, encoding initiator methionyl tRNA (tRNAiMet), or LHP1, encoding the yeast homolog of the human La autoantigen. The gcd10-504 mutation led to a reduction in steady-state levels of mature tRNAiMet, attributable to increased turnover rather than decreased synthesis of pre-tRNAiMet. Remarkably, the lethality of a GCD10 deletion was suppressed by high-copy-number IMT4, indicating that its role in expression of mature tRNAiMet is the essential function of Gcd10p. A gcd14-2 mutant also showed reduced amounts of mature tRNAiMet, but in addition, displayed a defect in pre-tRNAiMet processing. Gcd10p and Gcd14p were found to be subunits of a protein complex with prominent nuclear localization, suggesting a direct role in tRNAiMet maturation. The chromatographic behavior of elongator and initiator tRNAMet on a RPC-5 column indicated that both species are altered structurally in gcd10Delta cells, and analysis of base modifications revealed that 1-methyladenosine (m1A) is undetectable in gcd10Delta tRNA. Interestingly, gcd10 and gcd14 mutations had no effect on processing or accumulation of elongator tRNAMet, which also contains m1A at position 58, suggesting a unique requirement for this base modification in initiator maturation.

Adenosine↗

PubMed1998

Differential regulation of cardiac angiotensin converting enzyme binding sites and AT1 receptor density in the failing human heart.

BACKGROUND: The regulation and interaction of ACE and the angiotensin II (Ang II) type I (AT1) receptor in the failing human heart are not understood. METHODS AND RESULTS: Radioligand binding with 3H-ramiprilat was used to measure ACE protein in membrane preparations of hearts obtained from 36 subjects with idiopathic dilated cardiomyopathy (IDC), 8 subjects with primary pulmonary hypertension (PPH), and 32 organ donors with normal cardiac function (NF hearts). 125I-Ang II formation was measured in a subset of hearts. Saralasin (125I-(Sar1,Ile8)-Ang II) was used to measure total Ang II receptor density. AT1 and AT2 receptor binding were determined with the AT1 receptor antagonist losartan. Maximal ACE binding (Bmax) was 578+/-47 fmol/mg in IDC left ventricle (LV), 713+/-97 fmol/mg in PPH LV, and 325+/-27 fmol/mg in NF LV (P<0.001, IDC or PPH versus NF). In IDC, PPH, and NF right ventricles (RV), ACE Bmax was 737+/-78, 638+/-137, and 422+/-49 fmol/mg, respectively (P=0.02, IDC versus NF; P=0.08, PPH versus NF). 125I-Ang II formation correlated with ACE binding sites (r=0.60, P=0.00005). There was selective downregulation of the AT1 receptor subtype in failing PPH ventricles: 6.41+/-1.23 fmol/mg in PPH LV, 2.37+/-0.50 fmol/mg in PPH RV, 5.38+/-0.53 fmol/mg in NF LV, and 7.30+/-1.10 fmol/mg in NF RV (P=0.01, PPH RV versus PPH LV; P=0.0006, PPH RV versus NF RV). CONCLUSIONS: ACE binding sites are increased in both failing IDC and nonfailing PPH ventricles. In PPH hearts, the AT1 receptor is downregulated only in the failing RV.

Adenylyl Cyclases↗

PubMed1998

Role of endogenous interferon-gamma on the enhancement of splenic NK cell activity by electroacupuncture stimulation in mice.

Successive electro-acupuncture (EA) stimulation applied to bilateral anterior tibial muscles, where Zusanli (ST36) acupoints are located, once a day (30 min) for 3 successive days significantly enhanced splenic natural killer (NK) cell activity in BALB/c mice. The percentage of splenic NK cells, as measured by flow cytometry, was not affected in these mice. Interferon (IFN)-gamma level in splenic aqueous extract, prepared from the ST36 acupoint-stimulated mice, was significantly higher than that of the controls. In vivo treatment with neutralizing monoclonal antibody against mouse IFN-gamma completely abrogated the increase in splenic NK cell activity induced by ST36 acupoint stimulation. The same stimulation also significantly increased the concentration of splenic beta-endorphin, which coincided with the significant increase in splenic IFN-gamma production. Pre-administration of 10 mg/kg naloxone before initiation of EA stimulation every day reduced the enhancements of NK cell activity and IFN-gamma level. These observations strongly suggest that endogenous IFN-gamma mediates the up-regulation of NK cell activity by EA stimulation at the ST36 acupoints. Furthermore, endogenous beta-endorphin secreted by EA stimulation also plays an important role in the up-regulation of NK cell function, which may be realized through regulating IFN-gamma production.

Animals↗

PubMed1998

Copy number control of IncIalpha plasmid ColIb-P9 by competition between pseudoknot formation and antisense RNA binding at a specific RNA site.

Replication of a low-copy-number IncIalpha plasmid ColIb-P9 depends on expression of the repZ gene encoding the replication initiator protein. repZ expression is negatively controlled by the small antisense Inc RNA, and requires formation of a pseudoknot in the RepZ mRNA consisting of stem-loop I, the Inc RNA target, and a downstream sequence complementary to the loop I. The loop I sequence comprises 5'-rUUGGCG-3', conserved in many prokaryotic antisense systems, and was proposed to be the important site of copy number control. Here we show that the level of repZ expression is rate-limiting for replication and thus copy number, by comparing the levels of repZ expression and copy number from different mutant ColIb-P9 derivatives defective in Inc RNA and pseudoknot formation. Kinetic analyses using in vitro transcribed RNAs indicate that Inc RNA binding and the pseudoknot formation are competitive at the level of initial base paring to loop I. This initial interaction is stimulated by the presence of the loop U residue in the 5'-rUUGGCG-3' motif. These results indicate that the competition between the two RNA-RNA interactions at the specific site is a novel regulatory mechanism for establishing the constant level of repZ expression and thus copy number.

Bacterial Proteins↗

PubMed1998

Complex formation by all five homologues of mammalian translation initiation factor 3 subunits from yeast Saccharomyces cerevisiae.

The PRT1, TIF34, GCD10, and SUI1 proteins of Saccharomyces cerevisiae were found previously to copurify with eukaryotic translation initiation factor 3 (eIF3) activity. Although TIF32, NIP1, and TIF35 are homologous to subunits of human eIF3, they were not known to be components of the yeast factor. We detected interactions between PRT1, TIF34, and TIF35 by the yeast two-hybrid assay and in vitro binding assays. Discrete segments (70-150 amino acids) of PRT1 and TIF35 were found to be responsible for their binding to TIF34. Temperature-sensitive mutations mapping in WD-repeat domains of TIF34 were isolated that decreased binding between TIF34 and TIF35 in vitro. The lethal effect of these mutations was suppressed by increasing TIF35 gene dosage, suggesting that the TIF34-TIF35 interaction is important for TIF34 function in translation. Pairwise in vitro interactions were also detected between PRT1 and TIF32, TIF32 and NIP1, and NIP1 and SUI1. Furthermore, PRT1, NIP1, TIF34, TIF35, and a polypeptide with the size of TIF32 were specifically coimmunoprecipitated from the ribosomal salt wash fraction. We propose that all five yeast proteins homologous to human eIF3 subunits are components of a stable heteromeric complex in vivo and may comprise the conserved core of yeast eIF3.

Amino Acid Sequence↗

PubMed1998

Structure and transcriptional regulation of the human cystatin A gene. The 12-O-tetradecanoylphorbol-13-acetate (TPA) responsive element-2 site (-272 to -278) on cystatin A gene is critical for TPA-dependent regulation.

Cystatin A, a cysteine proteinase inhibitor, is one of the precursor proteins of cornified cell envelope of keratinocytes and is expressed during the late stage of keratinocyte differentiation. We have isolated and characterized the human cystatin A gene. The cystatin A gene consists of three exons and two introns. The first, the second, and the third exons consist of coding sequences that are 66, 102, and 126 base pairs in length, respectively. The first and the second introns consist of 14 and 3.6 kilobase pairs, respectively. The transcription initiation site was located 55 base pairs upstream from the first translation site. The fragment, +77 to -2595 in the 5'-flanking region of the human cystatin A gene, was subcloned into a chloramphenicol acetyltransferase (CAT) reporter vector. The expression vector, p2672CAT, produced a significant CAT activity in transiently transfected SV40-transformed human keratinocytes (SVHK cells), that were further stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent protein kinase C activator. Sequence analysis of the gene detected three TPA responsive elements (TRE-1, TRE-2, and TRE-3) and one AP-2 site on the 5' upstream promoter region. Deletion analyses of the p2672CAT vector demonstrated that TRE-2, which was located between -272 and -278, was critical for the regulation by TPA. Gel shift analyses revealed that c-Jun, JunD, and c-Fos bound to the TRE-2 region and that the p2672CAT activity level was elevated by co-transfection with c-Jun and c-Fos or with JunD and c-Fos expression vectors. Furthermore, co-transfection of SVHK cells with the protein kinase C-alpha expression vector and the p2672CAT expression vector also resulted in an increased CAT activity. These results indicate that the 5'-flanking region of the human cystatin A gene confers promoter activity and contains a TRE (TRE-2) that mediates, at least in part, the enhanced expression of this gene by TPA.

Amino Acid Sequence↗

PubMed1998

Antibodies specific for (6-4) DNA photoproducts: cloning, antibody modeling and construction of a single-chain Fv derivative.

We have investigated a series of four monoclonal antibodies that specifically recognize pyrimidine (6-4) pyrimidone photoproducts. One of these antibodies (64M4), bound all four possible pyrimidine-pyrimidone photoadducts with equal affinities whereas the others (64M2, 64M3 and 64M5) were selective for TC and TT sequences. In addition, 64M5 had the highest binding affinity for photodamaged DNA of the four [T. Mori et al., Photochem. Photobiol. 54 (1991) 225-232]. To help understand the differences between these antibodies, we have cloned and sequenced the variable region genes from all four. Comparing these sequences revealed that all four were highly similar to one another, although there were some differences in potential antigen-contact regions. To assess the influences of these sequence differences at the structural level, computer models were constructed for all four antibodies. Most of the sequence differences occurred in potential antigen contact regions, suggesting specific positions that might account for the observed differences in binding affinities and selectivities. A single-chain Fv derivative of 64M5 was therefore constructed and characterized to provide an experimental system in which structure-function relationships can be tested. This derivative could be isolated from Escherichia coli using two chromatographic steps and possessed the same binding specificity as the parent monoclonal antibody.

Amino Acid Sequence↗

PubMed1998

An RNA pseudoknot as the molecular switch for translation of the repZ gene encoding the replication initiator of IncIalpha plasmid ColIb-P9.

Translation initiation of the repZ gene encoding the replication initiator of plasmid ColIb-P9 is not only negatively regulated by the action of the antisense Inc RNA encoded in the leader region, but is also coupled to the translation and termination of a transcribed leader sequence, repY, a positive regulatory element for repZ gene expression. This translational coupling depends on base pairing between two complementary sequences, 5'-rGGCG-3' and 5'-rCGCC-3', which are located upstream of and in the middle of repY, respectively, and have the potential to form a pseudoknot with the stem-loop structure I. Another stem-loop called structure III near the 3'-end of repY sequesters both the 5'-rCGCC-3' sequence and the repZ ribosome-binding site. Here we show that the RepZ mRNA leader sequence synthesized in vitro indeed contains several stem-loop structures including structures I and III, but not the pseudoknot. However, disruption of structure III, without changing the repZ ribosome-binding site, by means of base substitution and deletion induces base pairing between the two short complementary sequences distantly separated, resulting in the formation of a pseudoknot. When the pseudoknot is allowed to form in vivo due to the same mutations, a maximum level of repZ expression is obtained comparable to one observed in the absence of Inc RNA. These results strengthen our previously proposed model that the pseudoknot induced by the translation and termination of the repY reading frame functions as the molecular switch for translational initiation of the repZ gene.

Bacterial Proteins↗