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S Lee

Publications and source records attributed to S Lee.

At least 1,063 records · Page 59Linked to original sources
PubMed1993

Differential expression of S1 and elongation factor-1 alpha during rat development.

Elongation factor-1 alpha (EF-1 alpha) is a highly conserved protein functioning in peptide elongation during translation. A cDNA, S1, was isolated; its deduced amino acid sequence shares high similarity with mammalian EF-1 alpha s (92%). While EF-1 alpha is present in all tissues, S1 mRNA can only be detected in brain, heart, and muscle. We report here that the retropseudogene phenomenon is attributable to EF-1 alpha and not S1, the latter being represented by a single copy in the rat genome. The S1 steady-state mRNA levels are consistently higher than EF-1 alpha in S1-positive tissues. S1 mRNA can only be detected late during brain, heart, and muscle development in vivo and increases to a plateau in early postnatal life. In a cultured muscle system, S1 expression is dependent upon the formation of myotubes, although the accumulation of S1 mRNA is significantly lower than that observed in adult skeletal muscle. EF-1 alpha mRNA levels are down-regulated during brain, heart, and muscle development, but stay relatively steady in liver. We show here that EF-1 alpha and S1 are differentially expressed during rat development and that the activation of S1 gene expression is subsequent to the terminal differentiation process in brain, heart, and muscle.

Amino Acid Sequence↗
PubMed1993

Complete coding sequence, intron/exon organization, and chromosomal location of the gene for the core I protein of human ubiquinol-cytochrome c reductase.

Core I protein is a nuclear-encoded component of the ubiquinol-cytochrome c reductase complex of the mitochondrial respiratory chain. We have located the gene for the human core I protein in the p21 region of chromosome 3, just upstream of the COL7A1 gene which encodes type VII collagen. The core I gene, which has been sequenced in its entirety, is comprised of 10,417 base pairs, from the major transcription start site to the polyadenylation signal, and contains 13 exons. The predicted polypeptide contains 480 amino acids, of which the first 34 are predicted to constitute a typical mitochondrial leader peptide containing 6 positively charged arginine residues. The predicted human protein shows significant homology with core I protein from Saccharomyces cerevisiae, rather high homology (64% similarity, 46% identity) with the processing enhancing protein, which functions as core I protein in Neurospora crassa, and, surprisingly, highest homology with the small subunit of the mitochondrial processing peptidase of rat (74% similarity, 55% identity). The predicted human sequence is 87% identical to the reported bovine core I sequence predicted from cDNA cloning, up to residue 298, but the two predicted sequences are widely divergent after that point.

Amino Acid Sequence↗
PubMed1993

Expression and identification of p90 as the murine mitochondrial glycerol-3-phosphate acyltransferase.

Glycerol-3-phosphate acyltransferase (GPAT) catalyzes the initial and committed step in glycerolipid biosynthesis. Mitochondrial GPAT, unlike the microsomal isozyme, prefers saturated fatty acids as a substrate. We have recently reported cloning of a cDNA to an unidentified 6.8-kb mRNA by a differential hybridization. The mRNA contains an open reading frame of 827 amino acids (p90) with 30% sequence homology in a 300 amino acid stretch to Escherichia coli GPAT. The 6.8-kb mRNA was induced dramatically when fasted mice were refed a high-carbohydrate diet. Here, we have expressed the open reading frame as trpE fusion proteins and used them to generate antibodies. The antibodies recognized a polypeptide of 90 kDa (p90) when the 6.8-kb cDNA sequence was used for in vitro transcription and translation. By Western blot analysis using these antibodies, we detected p90 in mitochondrial fractions of liver, and the p90 level was increased by refeeding. The increase in the p90 level correlated with the increase in mitochondrial GPAT activity. Moreover, p90 was not detectable in 3T3-L1 preadipocytes but markedly increased during adipose conversion. This increase was consistent with the 11-fold increase we observed in N-ethylmaleimide (NEM)-resistant mitochondrial GPAT activity during adipocyte differentiation. In addition, we have expressed p90 in CHO cells by stable transfection. The transfected genes in both correct and reverse orientations produced distinct 3.9-kb transcripts owing to the truncation of a part of the noncoding regions of the endogenous 6.8-kb mRNA before insertion into the pMSXND vector. The transfected CHO cells were treated with 2-aminopurine, an agent that increases expression of exogenous genes.(ABSTRACT TRUNCATED AT 250 WORDS)

3T3 Cells↗
PubMed1993

Effect of salts on conformational change of basic amphipathic peptides from beta-structure to alpha-helix in the presence of phospholipid liposomes and their channel-forming ability.

A synthetic model peptide, H-(Leu-Al alpha-Arg-Leu)3-(Leu-Arg-Al alpha-Leu)3-OH (4(6)) can form ion channels in planar lipid bilayers by taking an amphipathic alpha-helix (Agawa, Y., Lee, S., Ono, S., Aoyagi, H., Ohno, M., Taniguchi, T., Anzai, K. and Kirino, Y. (1991) J. Biol. Chem. 266, 20218-20222). For further study of ion channels formed by this type of peptides, we planned to synthesize [Trp1]-4(6)(Ser) and [Trp12]-4(6)(Ser) in which a hydrophilic amino acid, Ser, was introduced in several positions of 4(6) instead of hydrophobic ones. This modification was expected to decrease the ability of membrane perturbation and to simplify various current levels of the channel observed for 4(6). Furthermore, additional Trp was introduced to the N-terminus or position 12 to monitor the lipid-peptide interaction. CD study showed that both peptides formed a random structure in buffer, but an alpha-helix in the presence of egg PC and a beta-structure in egg PC/egg PG (3:1). Moreover, addition of NaCl to the acidic liposomes induced the conformational transition in the peptide from beta-structure to alpha-helix. Salt-induced conformational transition in the presence of acidic liposomes was discussed in terms of membrane binding and ion-channel formation in planar lipid bilayer. Despite introduction of hydrophilic residues instead of hydrophobic residues in 4(6), the peptide showed nearly the same dye-release ability from egg PC- egg PG liposomes as 4(6). [Trp12]-4(6)(Ser) was able to form cation-selective ion channels with two levels of conductance (mainly 250 and occasionally 125 pS) in asolectin planar lipid bilayer, suggesting that appropriate orientation of hydrophobic and hydrophilic residues in amphipathic peptide can simplify channel current levels.

Amino Acid Sequence↗
PubMed1993

Tumor aneuploidy in young patients with colorectal cancer.

BACKGROUND: Colorectal cancer in young patients (40 years of age or younger) often is considered to have a worse prognosis than in older patients. The authors studied tumor DNA status and stage of disease to determine whether tumors in younger patients behaved differently from tumors in older patients. METHODS: This retrospective study identified 33 young patients with colorectal cancer treated surgically between 1979 and 1989. The DNA content of the tumors was analyzed by DNA flow cytometry. Results were compared with 75 cases of colon cancer in patients older than 40 years of age. RESULTS: Six of the 33 young patients had inadequate tissue for study. Four patients with ulcerative colitis were excluded. Tumor aneuploidy was present in 14 of 23 young patients (61%; mean age, 35 years) and 46 of 75 older patients (61%; mean age, 71 years). When Dukes staging was performed for the young patients, one had Stage A (4%), nine had Stage B (39%), eight had Stage C (35%), and five had Stage D (22%) disease. The control group had similar staging. The distribution of aneuploid tumors within each Dukes stage was also similar. Twenty-one young patients were available for follow-up. Four (31%) of 13 patients with aneuploid tumors died, whereas none of 8 patients with diploid tumors died. This trend was not statistically significant (P < 0.10). CONCLUSIONS: The frequency of tumor aneuploidy, stage of disease at presentation, and distribution of tumor aneuploidy within each stage was similar when young and old patients with colorectal cancer were compared. There is a trend toward tumor aneuploidy being associated with a poorer prognosis in young patients.

Adult↗
PubMed1993

The human Kell blood group gene maps to chromosome 7q33 and its expression is restricted to erythroid cells.

The Kell blood group is one of the major antigenic systems in human red blood cells. To determine the location of the Kell gene on human chromosomes, panels containing genomic DNA of human-hamster somatic cell hybrids were hybridized with radiolabeled cDNA probe specific for the Kell locus. Only the samples containing DNA from chromosome 7 gave positive hybridization signals. In situ hybridization analysis, using genomic clones isolated with the cDNA, localized the KEL gene to 7q33. Northern blot analysis of poly(A)+ RNA from human brain, kidney, lung, fetal and adult liver, and bone marrow showed that Kell transcripts were only present in fetal liver and bone marrow. This indicates that the Kell protein, which carries the Kell antigens, may only be expressed in erythroid tissues.

Animals↗
PubMed1993

Antimicrobial specificity and hemolytic activity of cyclized basic amphiphilic beta-structural model peptides and their interactions with phospholipid bilayers.

We synthesized a series of cyclic antiparallel beta-sheet model peptides with various ring sizes, which were designed on the basis of a cyclic beta-structural antibiotic, gramicidin S (GS); cyclo(Val-Orn-Leu-D-Phe-Pro)2, and investigated in terms of their antimicrobial activity and specificity against Gram-positive and Gram-negative bacteria and lytic activity for human erythrocytes. In our planning, in order to compare the peptides with GS, D-Phe-Pro sequence forming beta-turn in GS molecule remained unaltered and repeating sequences of alternately hydrophobic (Leu)-hydrophilic (Orn) residue were introduced into the beta-structural parts. CD study in acidic liposomes as well as leakage study of carboxyfluorescein encapsulated in phospholipid vesicles indicated that the peptides strongly interacted with lipid bilayers by taking an amphiphilic beta-structure. Antimicrobial study showed that although GS is active only against Gram-positive bacteria, the antimicrobial spectra of the model peptides transformed gradually to be active against Gram-negative ones and finally only against Gram-negative bacteria whose repeating sequences increased. It should be noted that the designed cyclic model peptides show antibacterial activity but accompany no hemolysis. This indicates that an appropriate hydrophobicity together with a proper orientation of hydrophilic (cationic) and hydrophobic groups in cyclic beta-structural molecules can hold antimicrobial activity against both types of bacteria without damaging eukaryotic cells.

Amino Acid Sequence↗
PubMed1993

Translocation of TCR alpha chains into the lumen of the endoplasmic reticulum and their degradation.

After synthesis, the alpha chain of the T cell antigen receptor (TCR alpha) can form a complex with other TCR chains and move to the cell surface, or TCR alpha can undergo degradation in the endoplasmic reticulum (ER) if it remains unassembled. The mechanism of translocation and degradation in the ER is unclear. It was found that the putative transmembrane region of TCR alpha (alpha tm) was incompetent on its own to act as a transmembrane region. Molecules that contained alpha tm were translocated into the ER lumen and then underwent either rapid degradation or secretion, depending on the sequence of the cytoplasmic domain. A specific signal for ER degradation within alpha tm does not appear to be present.

Amino Acid Sequence↗
PubMed1993

Hole lifetimes in

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Journal Article↗
PubMed1993

A critical role for heat shock transcription factor in establishing a nucleosome-free region over the TATA-initiation site of the yeast HSP82 heat shock gene.

Heat shock genes are poised for rapid transcriptional activation in response to environmental stress. A universal structural characteristic of such genes is the presence of a nucleosome-free, DNase I hypersensitive promoter region. Here we investigate the structural and functional effects of mutating HSE1, the preferred heat shock factor (HSF) binding site upstream of the yeast HSP82 gene. In situ deletion or substitution of this sequence reduces both basal and induced transcription by at least two orders of magnitude. Moreover, such mutations lead to a dramatic transition in chromatin structure: the DNase I hypersensitive region is replaced by two stable, sequence-positioned nucleosomes. One of these is centered over the mutated heat shock element, while the other--as revealed by DNase I genomic footprinting--is precisely positioned in a rotational sense over the TATA-initiation site. Overexpression of yeast HSF strongly suppresses the null phenotype of the induced hsp82-delta HSE1 gene and re-establishes DNase I hypersensitivity over its promoter. Such suppression is mediated through sequence disposed immediately upstream of HSE1 and containing two low affinity heat shock elements. These data imply a critical role for HSF in displacing stably positioned nucleosomes in Saccharomyces cerevisiae and suggest that HSF transcriptionally activates HSP82 at least partly through its ability to alleviate nucleosome repression of the core promoter.

Base Sequence↗
PubMed1993

Effect of caval-portal shunt on ovarian tissue in rats: I. Histological observation.

Forty-three female Sprague Dawley rats were divided into five groups, with groups 1-4 subjected to end-to-side caval-portal shunt (CPS). In addition to CPS, group 1 (n = 13), group 2 (n = 10), and group 3 (n = 7) rats had undergone removal of the right ovary and one-half of the left ovary, the left ovary, and one-half of the left ovary, respectively. Group 4 (n = 6) rats were not subjected to ovariectomy. Group 5 (n = 7) animals were not subjected to CPS but underwent left ovarian hemiresection. The ovarian volume of the hemiresected ovaries increased to 393.00 +/- 4.83 mm3 and 126.00 +/- 44.3 mm3 from 18.40 +/- 0.54 mm3 and 18.40 +/- 0.59 mm in groups 1 and 3, respectively, at the end of three postoperative months. The nonresected ovaries enlarged to 339.98 +/- 5.09 mm3 and 226.3 +/- 46.2 mm3 from 36.79 +/- 1.09 mm3 in groups 2 and 3, respectively. When no ovaries were resected, the CPS animals in group 4 showed an increment of ovarian volume of 1.75-2.2 times as much as the preoperative ones. In the animals that had undergone simple hemiovariectomy (group 5), the contralateral ovaries showed a significant increase in volume (40.2 +/- 8.3 mm3 to 243.1 +/- 114.8 mm3) at 3 months. The hemiresected ovarian volume increased from 27.1 +/- 5.5 mm3 to 44.1 +/- 11.8 mm3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗