Biomedical subjects

Y Mao

Publications and source records attributed to Y Mao.

At least 73 records · Page 4Linked to original sources

PubMed2001

Protein kinase G activates the JNK1 pathway via phosphorylation of MEKK1.

We recently obtained evidence that treatment of human colon cancer cells with exisulind (sulindac sulfone) and related compounds induces apoptosis by activation of protein kinase G (PKG) and c-Jun kinase (JNK1). The present study further explores this mechanism. We demonstrate that in NIH3T3 cells a constitutively active mutant of PKG causes a dose-dependent activation of JNK1 and thereby transactivates c-Jun and stimulates transcription from the AP-1 enhancer element. The activation of JNK1 and the transactivation of c-Jun by this mutant of PKG were inhibited by a dominant negative MEKK1. In vitro assays showed that a purified PKG directly phosphorylated the N-terminal domain of MEKK1. PKG also directly phosphorylated a full-length MEKK1, and this was associated with enhanced MEKK1 phosphorylation. Thus, it appears that PKG activates JNK1 through a novel PKG-MEKK1-SEK1-JNK1 pathway, by directly phosphorylating and activating MEKK1.

3T3 Cells↗

PubMed2001

Cloning, expression, and characterization of a human inosine triphosphate pyrophosphatase encoded by the itpa gene.

ITP and dITP exist in all cells. dITP is potentially mutagenic, and the levels of these nucleotides are controlled by inosine triphosphate pyrophosphatase (EC ). Here we report the cloning, expression, and characterization of a 21.5-kDa human inosine triphosphate pyrophosphatase (hITPase), an enzyme whose activity has been reported in many animal tissues and studied in populations but whose protein sequence has not been determined before. At the optimal pH of 10.0, recombinant hITPase hydrolyzed ITP, dITP, and xanthosine 5'-triphosphate to their respective monophosphates whereas activity with other nucleoside triphosphates was low. K(m) values for ITP, dITP, and xanthosine 5'-triphosphate were 0.51, 0.31, and 0.57 mm, respectively, and k(cat) values were 580, 360, and 640 s(-1), respectively. A divalent cation was absolutely required for activity. The gene encoding the hITPase cDNA sequence was localized by radiation hybrid mapping to chromosome 20p in the interval D20S113-D20S97, the same interval in which the ITPA inosine triphosphatase gene was previously localized. A BLAST search revealed the existence of many similar sequences in organisms ranging from bacteria to mammals. The function of this ubiquitous protein family is proposed to be the elimination of minor potentially mutagenic or clastogenic purine nucleoside triphosphates from the cell.

Amino Acid Sequence↗

PubMed2001

Atp-bound topoisomerase ii as a target for antitumor drugs.

Topoisomerase II (TOP2) poisons interfere with the breakage/reunion reaction of TOP2 resulting in DNA cleavage. In the current studies, we show that two different classes (ATP-sensitive and -insensitive) of TOP2 poisons can be identified based on their differential sensitivity to the ATP-bound conformation of TOP2. First, in the presence of 1 mm ATP or the nonhydrolyzable analog adenosine 5'-(beta,gamma-imino)triphosphate, TOP2-mediated DNA cleavage induced by ATP-sensitive TOP2 poisons (e.g. doxorubicin, etoposide, mitoxantrone, and 4'-(9-acridinylamino)methanesulfon-m-anisidide) was 30-100-fold stimulated, whereas DNA cleavage induced by ATP-insensitive TOP2 poisons (e.g. amonafide, batracylin, and menadione) was only slightly (less than 3-fold) affected. In addition, ADP was shown to strongly antagonize TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive TOP2 poisons. Second, C427A mutant human TOP2alpha, which exhibits reduced ATPase activity, was shown to exhibit cross-resistance to all ATP-sensitive but not ATP-insensitive TOP2 poisons. Third, using ciprofloxacin competition assay, TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive poisons was shown to be antagonized by ciprofloxacin. These results suggest that ATP-bound TOP2 may be the specific target of ATP-sensitive TOP2 poisons. Using Lac repressor-operator complexes as roadblocks, we show that ATP-bound TOP2 acts as a circular clamp capable of entering DNA ends and sliding on unobstructed duplex DNA.

Adenosine Triphosphate↗

PubMed2001

A novel all helix fold of the AP180 amino-terminal domain for phosphoinositide binding and clathrin assembly in synaptic vesicle endocytosis.

Clathrin-mediated endocytosis plays a major role in retrieving synaptic vesicles from the plasma membrane following exocytosis. This endocytic process requires AP180 (or a homolog), which promotes the assembly and restricts the size of clathrin-coated vesicles. The highly conserved 33 kDa amino-terminal domain of AP180 plays a critical role in binding to phosphoinositides and in regulating the clathrin assembly activity of AP180. The crystal structure of the amino-terminal domain reported herein reveals a novel fold consisting of a large double layer of sheets of ten alpha helices and a unique site for binding phosphoinositides. The finding that the clathrin-box motif is mostly buried and lies in a helix indicates a different site and mechanism for binding of the domain to clathrins than previously assumed.

Adaptor Proteins, Vesicular Transport↗

PubMed2001

Cloning and characterization of a novel human leptin receptor overlapping transcript-like 1 gene (LEPROTL1).

A new full-length cDNA encoding a novel protein was isolated from our human fetal brain cDNA library. The cDNA consists of 2701 bp and has a putative open reading frame encoding 131 amino acids which possesses a JAK binding site (Pro(46)-Ile-Pro(48) which is preceded by a cluster of hydrophobic residues) and is highly homologous to the leptin receptor gene-related protein (OB-RGRP). Northern blot analysis showed that this new gene is widely expressed in human tissues and radiation hybrid mapping placed the gene to human chromosome 8p21.1-8p21.2.

Amino Acid Sequence↗

PubMed2001

Lifetime residential and workplace exposure to environmental tobacco smoke and lung cancer in never-smoking women, Canada 1994-97.

Although the risk of lung cancer among never-smokers living with a spouse who smokes has been extensively studied, the impact of lifetime residential and workplace environmental tobacco smoke has received less attention. As part of a large population-based case-control study of lung cancer, we collected lifetime residential and occupational passive smoking information from 71 women with lung cancer and 761 healthy control subjects, all of whom reported being lifetime nonsmokers. The adjusted odds ratio (OR) for lung cancer associated with residential passive exposure only was 1.21 (95% confidence interval [CI] 0.5-2.8). Although more years of and more intense residential passive smoke exposure tended to be associated with higher risk estimates, no clear dose-response relationship was evident. The OR for women with passive exposure as a child and as an adult was 1.63 (95% CI 0.8-3.5) and for those only exposed as an adult 1.20 (95%CI 0.5-3.0). Exposure to environmental tobacco smoke only in the workplace was associated with an adjusted OR of 1.27 (95% CI 0.4-4.0). Risks associated with increasing occupational exposure year tertiles were 1.24, 1.71 and 1.71. Total smoker-years of residential and occupational exposure combined resulted in a statistically significant trend (linear test for trend p = 0.05) with ORs for tertiles of exposure of 0.83, 1.54 and 1.82. Our results are consistent with the literature suggesting that long-term, regular exposure to either residential or occupational environmental tobacco smoke is associated with increased lung cancer risk in never-smoking women.

Adult↗

PubMed2001

Attitude of Chinese orthodontists towards the relationship between orthodontic treatment and temporomandibular disorders.

OBJECTIVE: To determine the attitude of some Chinese orthodontists towards the relationship between orthodontic treatment and temporomandibular disorders (TMDs). SUBJECTS AND METHODS: 25 orthodontists, in six public hospitals (Xi'an, the capital of Shaanxi Province, China), were asked to complete a 10-item questionnaire concerning orthodontics/TMD. RESULTS: 84% of orthodontists often asked their patients about the signs and symptoms of TMD before orthodontic treatment and 92% reported examining the TMJ region. 76% of orthodontists thought orthodontic treatment may possibly lead to a greater incidence of TMD, while 84 per cent claimed that orthodontic treatment might prevent TMD. Methods of orthodontic treatment, patient's age, and occlusal interference were regarded as risk factors leading to increased incidence of TMD. CONCLUSIONS: Some Chinese orthodontists realise the importance of the relationship between orthodontic treatment and TMD. Most thought that unsuitable orthodontic treatment might increase the development of TMD and that orthodontic treatment could prevent TMD.

Adult↗

PubMed2001

Increased throughput in quantitative bioanalysis using parallel-column liquid chromatography with mass spectrometric detection.

The feasibility of quantitative bioanalysis by parallel-column liquid chromatography in conjunction with a conventional single-source electrospray mass spectrometer has been investigated using plasma samples containing a drug and its three metabolites. Within a single chromatographic run time, sample injections were made alternately onto each of two analytical columns in parallel at specified intervals, with a mass spectrometer data file opened at every injection. Thus, the mass spectrometer collected data from two sample injections into separate data files within a single chromatographic run time. Therefore, without sacrificing the chromatographic separation or the selected reaction monitoring (SRM) dwell time, the sample throughput was increased by a factor of two. Comparing the method validation results obtained using the two-column system with those obtained using the corresponding conventional single-column approach, the methods on the two systems were found to be equivalent in terms of accuracy and precision. The parallel-column system is simple and can be implemented using existing laboratory equipment with no additional capital outlays. A parallel-column system configured in this manner can be used not only for the within-a-run analysis of two samples containing two different sets of chemical entities, but also for the within-a-run analysis of two samples containing the same set of chemical entities.

Chromatography, Liquid↗

PubMed2001

Identification of a new gene product of PKIbeta by HPLC-ESIMS.

An identification method using high-performance liquid chromatography combined with electrospray mass spectrometry (HPLC-ESIMS) has been developed to verify an expressed gene product of kinase inhibitor (PKIbeta). This protein was expressed in this university for the first time from a newly cloned gene in the cDNA library of human fetal brain. The measured MW (8468.9 Da) of PKIbeta-78 was consistent with expectations. The gene product of PKIbeta-78 was monitored by ESIMS to ensure there was no mis-expressed PKIbeta-70 in the process of gene engineering. The peptide mapping of PKIbeta-78 and its partial sequence were, furthermore, determined. By database searching based on the experimental MWs and partial sequences provided, it was verified that this gene product is a new protein. The pseudosubstrate site and leucine-rich site for the function region of PKIbeta-78 are also confirmed.

Amino Acid Sequence↗

PubMed2001

Monitoring of bio-oxidation process of ferrous ion by using piezoelectric impedance analysis.

A new method of monitoring the bio-oxidation process of ferrous ion in the presence of Thiobacillus ferroxidans was proposed by piezoelectric impedance analysis. The time courses of the responses of impedance parameters for a quartz crystal in a culture system were simultaneously obtained and discussed. It was found that the frequency shift response originates mainly from the adsorption of bacterial metabolites on the surface of gold electrode. Experiments also examined the effect of culture temperature on the bio-oxidation process. Combined with the growth situation of the bacterium, an impedance response model reflecting the process was established. By fitting Delta f vs. time curves toward the proposed model, we obtained and discussed the bacterial growth parameters. The results showed that the proposed method could provide real time and multidimensional information to monitoring of the bio-oxidation process.

Acidithiobacillus thiooxidans↗

PubMed2001

Cloning and characterization of a human lysyl oxidase-like 3 gene (hLOXL3).

Using the PCR primers generated from human expressed sequence tag (EST), the cDNA of lysyl oxidase-like gene 3 (LOXL3), a new member of human lysyl oxidases gene family, was cloned from the human fetal brain mRNA. The predicted amino acid sequence of the hLOXL3 gene was highly homologous to mLOR2. Bioinformatics analysis shows that hLOXL3 protein is also a member of the scavenger receptor cysteine-rich family, which contains a 25 amino acids signal peptide. The hLOXL3 gene was mapped to human 2p13 locus by BLAST search and at least 14 exons were found. Expression of the hLOXL3 gene was detected in several human tissues and especially high in spleen and testis.

Amino Acid Oxidoreductases↗

PubMed2001

PDZ-binding kinase participates in spermatogenesis.

A cDNA clone denoted SPK (spermatogenesis-related protein kinase) was isolated from human fetal brain cDNA library. The deduced protein was 99% identical to human PDZ-binding kinase (PBK), which is a mitotic kinase. Its isoform, which is about 300 bp longer at 3' end, was also isolated in this study. SPK gene was assigned to human chromosome 8p21.2 by radiation hybrid. Northern blot analysis indicated that SPK mRNA was predominantly expressed in testis. SPK mRNA was localized to the outer cell layer of seminiferous tubules by in situ hybridization, suggesting involvement of it in the process of spermatogenesis.

Amino Acid Sequence↗

PubMed2001

Cloning and characterization of a novel human TEKTIN1 gene.

Tektins comprise a family of filament-forming proteins that are known to be coassembled with tubulins to form ciliary and flagellar microtubules. A new member of the tektin gene family was cloned from the human fetal brain cDNA library. We hence named it the human TEKTIN1 gene. TEKTIN1 cDNA consists of 1375 bp and has a putative open reading frame encoding 418 amino acids. The predicted protein is 48.3 kDa in size, and its amino acid sequence is 82% identical to that of the mouse, rat, and dog. One conserved peptide RPNVELCRD was observed at position number 323-331 of the amino acid sequence, which is a prominent feature of tektins and is likely to represent a functionally important protein domain. TEKTIN1 gene was mapped to the human chromosome 17 by BLAST search, and at least eight exons were found. Northern blot analysis indicated that TEKTIN1 was predominantly expressed in testis. By in-situ hybridization analysis, TEKTIN1 mRNA was localized to spermatocytes and round spermatids in the seminiferous tubules of the mouse testis, indicating that it may play a role in spermatogenesis.

Amino Acid Sequence↗

PubMed2001

15alpha-acetoxycleomblynol A from Cleome amblyocarpa.

Reinvestigation of the MeOH-CH(2)Cl(2) extract of the aerial parts of Cleome amblyocarpa led to isolation of a new dammarane triterpenoid, 15alpha-acetoxycleomblynol A, whose structure was determined to be 11alpha,15alpha-diacetoxybrachycarpon-22(23)-ene (1) by NMR data interpretation and X-ray analysis.

Crystallography, X-Ray↗

PubMed2001

Cloning and characterization of KLHL5, a novel human gene encoding a kelch-related protein with a BTB domain.

Most kelch family proteins contain two conserved domains, the BTB domain and the kelch repeat domain. Here we describe the cloning and characterization of a novel human KLHL5 gene. The 3488 bp cDNA encodes a kelch family protein homologous to the Drosophila kelch protein. It also contains the two conserved domains. Northern blot analysis reveals a single transcript. It is abundantly expressed in ovary, adrenal gland, and thyroid and less abundantly expressed in trachea, prostate, testis, lymph node, and spinal cord. KLHL5 was mapped to 4p13-4p15.1.

Amino Acid Sequence↗

PubMed2001

Identification of a human LNX protein containing multiple PDZ domains.

Recently PDZ domains have been recognized as crucial organizers of protein complexes at the plasma membrane. Here we report the cloning of a novel 3.7-kb cDNA LNX from a human fetal brain cDNA library. The deduced amino acid sequence shares about 88% identity with the p70 form of Lnx, which is the mouse ligand of Numb protein X. Motif analysis reveals five protein-interaction modules conservative to those in the Lnx protein, including four PDZ domains and a NPXY motif for binding of the Numb PTB domain. Northern blot analysis shows that the length of the transcript in brain is distinct from those in other tissues. By radiation hybrid mapping, we localize the LNX gene to human chromosome 4q12 between marker D4S1577 and marker D4S1594. We predict that LNX may be important for the organization of signaling complexes in Numb-involved pathways or pathways regulated by other PTB-containing proteins.

Amino Acid Motifs↗

PubMed2001

Incidence of second primary breast cancer among women with a first primary in Manitoba, Canada.

Second primary breast cancer is of importance because of the increasing incidence of first primary breast cancer and improved survival. There is lack of information on the disease in Canada. We studied 14,220 women with a first primary breast cancer (invasive only) diagnosed during the period from 1970 to 1997, in Manitoba, Canada. A breast cancer was considered to be a second primary if it was an invasive lesion diagnosed at least six months after the diagnosis of an initial primary breast cancer. The incidence rate of second primary breast cancer was approximately six per 1,000 person-years, and the cumulative incidence during the 28-year study period was 14.3%. Average age at diagnosis of first primary breast cancer had increased significantly since 1970. The incidence was higher in 1975-1979, and there was no significant difference among other study periods after adjustment for the age at diagnosis of first primary breast cancer. Standardized incidence ratios showed no significant difference among six age groups after adjusting for calendar year. However, women with a first primary breast cancer had an increased risk of developing a second primary breast cancer compared with the risk of developing a first primary breast cancer among the general female population. The SIR was markedly greater among women who had a first primary breast cancer before the age of 40 years, and decreased significantly with increasing age at diagnosis of first primary breast cancer. The data provide epidemiological information on second primary breast cancer risk for the general female population in Manitoba, Canada.

Adult↗

PubMed2001

Molecular cloning and characterization of a novel Dehydrogenase/reductase (SDR family) member 1 genea from human fetal brain.

Short-chain dehydrogenases/reductases (SDR) constitute a large protein family of NAD(P)(H)-dependent oxidoreductase. They are defined by distinct, common sequence motifs and show a wide range of substrate specialisms. By large-scale sequencing analysis of a human fetal brain cDNA library, we isolated a novel human SDR-type dehydrogenase/reductase gene named Dehydrogenase/reductase (SDR family) member 1 (DHRS1). The DHRS1 cDNA is 1411 base pair in length, encoding a 314-amino-acid polypeptide which has a SDR motif. Northern blot reveals two bands, of about 0.9 and 1.4 kb in size. These two forms are expressed in many tissues. The DHRS1 gene is localized on chromosome 14q21.3. It has 9 exons and spans 9.2 kb of the genomic DNA.

Amino Acid Sequence↗