Activation of CYP11A and CYP11B gene promoters by the steroidogenic cell-specific transcription factor, Ad4BP

We have examined the transcriptional activity of four cis-elements, Ad1(CRE), Ad2, Ad3, and Ad4, that are present in the promoter of the bovine CYP11B (11 beta-hydroxylase P-450) gene using beta-globin reporter gene constructs and transient transfection into steroidogenic and nonsteroidogenic cell types. Only Ad1(CRE), a CRE homolog, showed forskolin-dependent transcriptional activity in adrenal tumor Y-1 cells, whereas the other elements were not able to stimulate transcription by themselves. As Ad3 and Ad4 had previously been identified as the cis-elements required for full cAMP-dependent transcription of this gene, we examined the effect of combinations of different cis-elements on the transcription of the reporter gene. In Y-1 cells, Ad1(CRE) and four tandem copies of any one of the other cis-elements substantially activated transcription in response to forskolin treatment. The template carrying Ad1(CRE) and Ad4 was also active in testicular Leydig cells, I-10, whereas it was inactive in nonsteroidogenic PC-12 cells. Transcriptional activation by the 4xAd4/Ad1(CRE) combination presumably depended on the presence of Ad4-binding protein (Ad4BP), which is absent in PC-12 cells, as shown by immunoblot analysis. This was confirmed by cotransfecting an expression vector for Ad4BP into PC-12 cells, which caused forskolin-dependent transcription to increase in proportion to the amount of expression vector. In Y-1 cells, transcriptional activation by forskolin was mimicked by cotransfection of an expression vector for the catalytic subunit of protein kinase-A.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular cloning and characterization of a human carboxylesterase gene

A cDNA encoding human liver carboxylesterase and its gene were isolated. Nucleotide sequence analyses of the cDNA revealed that the predicted enzyme protein consists of 567 amino acids, including 18 amino acids of a putative signal peptide. Comparison of the deduced amino acid sequences of this enzyme with those of seven other carboxylesterases in various mammalian species, together with experimental data from several other laboratories, showed that these enzymes can be classified into three groups depending on the sequences at their carboxyl terminals and the presence or absence of one exon. A human carboxylesterase gene was found to span approximately 30 kb and to have 14 small exons. Alignments of this gene with those of human cholinesterase and rat cholesterol esterase indicated insertional sites at some introns and homologous amino acid sequences around them, although these genes have different numbers of exons. Thus the results supported the conclusion that these esterases evolved from a common ancestral gene.

Ad4BP regulating steroidogenic P-450 gene is a member of steroid hormone receptor superfamily

Bovine cytochrome P-450(11 beta) gene (CYP11B) has six different cis-acting elements, Ad1, Ad2, Ad3, Ad4, Ad5, and Ad6, in the promoter region. The Ad4 site also exists in the promoter regions of other steroidogenic P-450 genes as well as in CYP11B1. An Ad4-binding protein (Ad4BP) which specifically binds to the Ad4 site was purified from bovine adrenal cortex nuclear extract, and its molecular mass was 53 kDa. A complementary DNA encoding Ad4BP was isolated from a bovine adrenal cortex cDNA library. The cDNA clone contained an open reading frame of 1383 base pairs encoding 461 amino acids, whose calculated molecular weight was 51,020. The predicted amino acid sequence of Ad4BP revealed that the protein has a zinc finger domain and a ligand binding/dimerization domain. Ad4BP is a novel member of the steroid hormone receptor superfamily. Comparison of the primary structures of the hormone receptor superfamily showed that Ad4BP was highly homologous to FTZ-F1, which regulates the fushi tarazu gene, and ELP, which is expressed in the murine embryonal carcinoma cells. Transfection of a Ad4BP expression plasmid into CV-1 cells activated the transcription of the CAT reporter gene carrying the Ad4 sequence in the promoter region.

A mitochondrial import factor purified from rat liver cytosol is an ATP-dependent conformational modulator for precursor proteins

Rat liver cytosol contained an activity that stimulated the import of wheat germ lysate-synthesized precursor proteins into mitochondria. The activity was purified 10,000-fold from the cytosol as a homogeneous heterodimeric protein. This protein (termed mitochondrial import stimulation factor or MSF) stimulated the binding and import of mitochondrial precursor proteins. MSF was also found to recognize the presequence portion of mitochondrial precursors and catalyze the depolymerization and unfolding of in vitro synthesized mitochondrial precursor proteins in an ATP-dependent manner; in this connection, MSF exhibited ATPase activity depending on the important-incompetent mitochondrial precursor protein. The mitochondrial binding and import-stimulating activities were strongly inhibited by the pretreatment of MSF with NEM, whereas the ATP-dependent depolymerization activity was insensitive to the NEM treatment, suggesting that the process subsequent to the unfolding was inhibited with the NEM treatment. We conclude that MSF is a multifunctional cytoplasmic chaperone specific for mitochondrial protein import.

Three forms of rat CYP11B genes: 11 beta-hydroxylase gene, aldosterone synthase gene, and a novel gene

We isolated three genomic clones of rat P-450(11 beta) genes (CYP11B). Two of them corresponded to 11 beta-hydroxylase gene (CYP11B1) and aldosterone synthase gene (CYP11B2), respectively. The third one was a novel gene resembling both CYP11B1 and CYP11B2, and was named CYP11B3 gene (CYP11B3). CYP11B2 and CYP11B3 are located tandemly in the genome in the same direction approximately 24 kb apart. These three genes were highly homologous in their amino acid coding regions, with 88% (CYP11B1 to CYP11B2), 89% (CYP11B2 to CYP11B3), 96% (CYP11B1 to CYP11B3) nucleotide identity. The numbers and the locations of the exons of these three genes also exactly corresponded to each other. However, the nucleotide sequences of the 5' upstream regions of CYP11B1 and CYP11B2 were significantly different, suggesting different transcriptional regulations. CYP11B3 had almost the same sequence as CYP11B1 gene in the 5' upstream region. A putative Ad4 site, a cis-acting element present in the promoter regions of all the steroidogenic P-450s so far reported [Morohashi, K., Honda, S., Inomata, Y., Handa, H., Omura, T. (1992) J. Biol. Chem. 267, 17913-17919], was found in the promoter regions of both CYP11B1 and CYP11B2. Gel retardation analysis showed the binding of Ad4BP purified from bovine adrenal cortex to these two Ad4 sites. We analyzed the relative abundance of the mRNAs corresponding to these three genes by the generation of RT-PCR libraries from rat adrenal total RNAs.(ABSTRACT TRUNCATED AT 250 WORDS)

An isozyme of microsomal carboxyesterases, carboxyesterase Sec, is secreted from rat liver into the blood

It is generally believed that liver carboxyesterases are localized exclusively in the endoplasmic reticulum (ER), mostly in the lumen, loosely bound to the inner side of the membrane. A cDNA clone, clone (8-1/2-1) supposed to code for one of the isozymes, carboxyesterase E1, was isolated by Takagi et al. [J. Biochem. 104, 801-806 (1988)]. However, the protein coded by clone (8-1/2-1) had no consensus ER retention signal at its carboxy terminus, and the mechanism of its retention by ER lumen was unclear. When clone (8-1/2-1) was expressed in COS cells in this study, the plasmid-coded protein was secreted into the medium. When the carboxy terminal portion of the clone (8-1/2-1)-coded protein was replaced with the corresponding region of another carboxyesterase, pI 6.1 esterase, which had the HVEL sequence at the carboxy terminus, the chimeric protein was retained in the COS cells. We searched for a secretory form carboxyesterase in rat blood immunochemically using polyclonal antibodies to carboxyesterase E1, and detected a cross-reacting protein with a molecular weight of 68 kDa. The molecular weight was decreased by endoglycosidase F treatment but not by endoglycosidase H treatment, indicating that the protein carries complex type sugar chains. In addition, the cross-reacting protein was labeled with [3H] diisopropylfluorophosphate (DFP), suggesting that the protein has an esterase-type active center serine.(ABSTRACT TRUNCATED AT 250 WORDS)

Accelerated rejection of allografted rat liver perfused with anti-ICAM-1 monoclonal antibody

Infusion of mouse anti-rat ICAM-1 into the portal vein of ACI rat liver graft before transplantation resulted in accelerated rejection by LEW recipients (2.9 +/- 2.5 days), when compared to the ACI liver grafts perfused with either Lactate-Ringer's solution (9.8 +/- 1.3) or anti-human ICAM-1 mAb (9.8 +/- 3.1). Histologic features of anti-rat ICAM-1 perfused grafts were spotty ischemic necrosis, whereas those of control grafts were marked cellular infiltration. These combined survival and histologic data suggest that the accelerated rejection may be mediated by vascular deterioration.

Cooperative transcription activation between Ad1, a CRE-like element, and other elements in the CYP11B gene promoter

We previously reported the presence of six different cis-acting elements (Ad1 to Ad6) in the promoter region of the bovine CYP11B gene. Although the Ad1 site (TGACGTGA) was similar to a palindromic CRE (TGACGTCA), two other upstream sequences, Ad3 and Ad4, were identified as the cAMP response sequences of the gene. We analyzed the functional relationship between the Ad1 site and the upstream elements. Mutation analyses of the Ad1 site indicated that the 5' half of the site (TGACG) was important for the transcription of the gene in vitro. In Y-1 cells, a plasmid with a mutated Ad1 showed no response to cAMP. The effect of the mutation at the Ad1 site on the cAMP response was almost the same as that of the deletion of Ad3 and Ad4, although the role of each element seemed to be different. These results indicated that both the Ad1 site and the upstream elements, Ad3 and Ad4, were necessary for the full response to cAMP of the CYP11B gene. When the Ad1 site in the promoter region was replaced with a palindromic CRE, elevated transcription activity was detected both in vitro and in vivo. Two kinds of CREBs (43 and 47 kDa) purified from a HeLa cell nuclear extract bound to the Ad1 site. The binding of the palindromic CRE to the nuclear factor(s) was stronger than that of Ad1.

A common trans-acting factor, Ad4-binding protein, to the promoters of steroidogenic P-450s

Previous studies of bovine CYP11B1 gene regulation revealed six cis-acting elements, Ad1, Ad2, Ad3, Ad4, Ad5, and Ad6, in the 5' upstream region of the gene. Ad4 site was a positive transcription element in the stimulation by cAMP. Ad4-binding protein (Ad4BP) was purified from the nuclear extract of bovine adrenal cortex using affinity latex particles conjugated with polymerized Ad4 sequences. The molecular mass of the purified Ad4BP estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was approximately 53 kDa. To characterize the binding specificity of Ad4BP, oligonucleotides homologous to Ad4 sequence and AGGTCA containing sequences in the promoter regions of steroidogenic P-450s were synthesized and used for gel shift analyses as competitors. The competition experiments revealed that Ad4BP bound not only to (C/T)CAAGG(T/C)(C/T), which was originally identified as the Ad4 binding site, but also to (Pu)PuPuAGGTCA. All the steroidogenic P-450 genes examined had at least one Ad4BP binding sequence. Experiments with model sequences containing various nucleotide substitutions established that (C/T)CAAGG(T/C)CA is the strongest binding sequence for Ad4BP. The expression of Ad4BP was examined with adrenal cortex cells and several other steroidogenic and nonsteroidogenic cells. Only the steroidogenic cells, the granulosa cells of bovine ovary, and I-10 cells derived from mouse Leydig cells, expressed the binding activity to Ad4 site. The presence of Ad4 site as a common cis-acting element in the genes of all the steroidogenic P-450s and the steroidogenic tissue-specific expression of Ad4BP strongly suggests that Ad4BP is an indispensable transcription factor for the expression of all the steroidogenic P-450 genes.

Mitochondrial porin can be translocated across both endoplasmic reticulum and mitochondrial membranes

Mitochondrial porin is a major integral membrane protein of the outer membrane. To assess the stop-transfer sequence in the yeast porin molecule (P), we constructed the following chimeric proteins. (i) The signal sequence of interleukin 2, a secretory protein, was fused to the amino-terminus of porin (SP). (ii) The matrix targeting presequence of cytochrome c oxidase subunit IV was fused to the amino-terminus of porin (CP). (iii) The amino-terminal segment consisting of 42 amino acid residues of "70 kDa protein" of yeast mitochondria, a major membrane protein of the outer membrane, was introduced into the middle portion of interleukin 2 (IL70). These chimeric proteins were expressed with an in vitro transcription-translation system and their integration into microsomal membrane or mitochondrial membranes was examined. When the proteins were synthesized in vitro with wheat germ cell-free system in the presence of rough microsomal membrane (RM), SP was completely translocated across the membrane, processed by the signal peptidase, and glycosylated. The translocation of IL70 molecule across RM was stopped at the introduced amino-terminal segment of 70 kDa protein. The authentic porin did not interact with the microsomal membrane. To assess the interaction with mitochondria, porin and CP were synthesized with the reticulocyte lysate system and subjected to posttranslational import reaction with isolated rat liver mitochondria. The authentic porin was integrated into the outer membrane in an alkali-resistant fashion. CP was imported into the mitochondria and its presequence was cleaved by the processing protease in the matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of adrenodoxin precursor expressed in Escherichia coli

The precursor of bovine adrenodoxin (pAd), a mitochondrial protein, was expressed in Escherichia coli. The cloned cDNA of pAd was ligated to an expression vector pET-3d, and silent mutations were introduced into the N-terminal portion of the cDNA in order to increase the expression. The precursor was highly expressed (approximately 20% of the total cell protein) as the inclusion body, and contained an iron-sulfur center as judged from its optical absorption spectra. The inclusion body was solubilized with 7 M urea and pAd was purified in the presence of urea. The purified pAd was efficiently imported into isolated bovine adrenal cortex mitochondria and processed to the mature form. The import reaction required ATP inside the mitochondria in addition to the inner membrane potential, and was strongly inhibited by trypsin treatment of the mitochondria, as in the case of the in vitro translated precursor. It was, however, not dependent on the unfolding activity of the cytosolic factor with extramitochondrial ATP.

Nucleotide sequence of capsid protein gene of rice tungro bacilliform virus

The sequence of 5,028 nucleotides, including one open reading frame (ORF), of rice tungro bacilliform virus (RTBV) dsDNA was determined. The predicted translational product comprises 1,675 amino acids and has Mr of 194,134 (p194). The amino acid sequences of three tryptic fragments from the 32 k capsid protein of RTBV (p32) were found in the predicted translational product indicating that the ORF codes for the RTBV capsid protein.

Functional expression of cDNAs for bovine 11 beta-hydroxylase-aldosterone synthases, P450(11 beta)-2 and -3 and their chimeras

Two molecular species of bovine P450(11 beta), P450(11 beta)-2 and P450(11 beta)-3 have been identified, in which the amino acid differences were found at the 6th, 36th and 82nd positions from the NH2-termini of the mature proteins. They catalyzed the 11 beta-, 18- and 19-hydroxylation and aldosterone formation from 11-deoxycorticosterone, and the rate of production of 18-hydroxycorticosterone and aldosterone by P450(11 beta)-3 was greater than that by P450(11 beta)-2 [Morohashi et al., J. Biochem. 107 (1990) 635-640]. In this study, chimeric clones were constructed whose 6th, 36th and 82nd amino acid residues were exchanged with each other. Two original clones and six chimeric clones were expressed in COS-7 cells, and their steroidogenic activities studied. The ratio of aldosterone or 18-hydroxycorticosterone production to corticosterone production by one clone was compared with that of the other. The ratios for the four clones having Gly36 [P450(11 beta)-3 type] were 0.08-0.22, whereas those for the clones having Ser36 [P450(11 beta)-2 type] were 0.03-0.05, suggesting that the Gly36 structure is important for aldosterone production.

Functions of signal and signal-anchor sequences are determined by the balance between the hydrophobic segment and the N-terminal charge

The signal sequence of secretory proteins and the signal-anchor sequence of type II membrane proteins initiate the translocation of the following polypeptide segments, whereas the signal-anchor sequence of cytochrome P-450-type membrane proteins mediates the membrane insertion of the polypeptide via a signal-recognition particle-dependent mechanism but does not lead to the translocation of the following C-terminal sequences. To establish the structural requirements for the function of signal and signal-anchor sequences, we constructed chimeric proteins containing artificial topogenic sequences in which the N-terminal net charge and the length of the hydrophobic segment were systematically altered. Utilizing an in vitro translation-translocation system, we found that hydrophobic segments consisting of 7-10 leucine residues functioned as signal sequences whereas segments with 12-15 leucine residues showed different topogenic functions, behaving as signal sequences or P-450-type signal-anchor sequences, depending on the N-terminal charge. From these observations, we propose that the function of N-terminal topogenic sequences depends on a balance between the N-terminal charge and the length of the following hydrophobic segment.

Nucleotide sequences of genome segments S8, encoding a capsid protein, and S10, encoding a 36K protein, of rice gall dwarf virus

The nucleotide sequences of DNAs complementary to the eighth (S8) and the tenth (S10) largest of the 12 genome segments of rice gall dwarf virus (RGDV) were determined. The S8 and S10 segments consist of 1578 and 1198 nucleotides, each with a single open reading frame extending for 1278 nucleotides from nucleotide 21, and 960 nucleotides from nucleotide 22, respectively. S8 encodes a polypeptide of 426 amino acids with an Mr of 47419. The amino acid sequences of several peptide fragments of the major outer capsid protein reported as 45K were contained in the predicted polypeptide. This protein, renamed the 47K protein, showed high homology with the outer capsid proteins of rice dwarf virus (RDV) and wound tumour virus (WTV); there was 56, 52 and 48% amino acid sequence identity between RGDV and WTV, RGDV and RDV, and RDV and WTV, respectively. S10 had the coding potential for a polypeptide of 320 amino acids with an Mr of 36,095 (36K protein), which exhibits 32% and 35% amino acid sequence identity with the predicted translation product of RDV S9 and the P9 capsid protein encoded by WTV S11, respectively. The conserved terminal sequences 5' GG...GAU 3' which are present in all genome segments of WTV and RDV so far analysed, and in S9 of RGDV, were also found in RGDV S8 and S10. This conserved sequence together with the segment-specific inverted repeats found in the terminal sequence of RGDV S8 and S10 are thus characteristic structures common to all three phytoreoviruses. The nucleotide sequence of the region surrounding the inverted repeats was more similar between RGDV and WTV than between RGDV and RDV.

A reovirus in the brown planthopper, Nilaparvata lugens

A new virus, belonging to the reovirus group, was found in an apparently healthy colony of the brown planthopper, Nilaparvata lugens, and was referred to as the Nilaparvata lugens reovirus (NLRV). The virus was found in the cytoplasm of the insect cells, sometimes associated with tubular structures, which is one of the characteristic features in tissues infected with reoviruses. The virus was purified by carbon tetrachloride clarification, polyethylene glycol precipitation, differential and CsCl equilibrium centrifugations. The virus has double-shelled particles approximately 65 nm in diameter, containing 10 genome segments of dsRNA. The electrophoretic profile of the dsRNA segments differed from those of viruses associated with rice planthoppers and leafhoppers. Seven proteins were detected in a purified preparation of the virus: four were associated with the core particle and three with the outer shell. A virus antigen was detected in individual insects by ELISA. The virus is retained after injection and is vertically transmitted to the offspring.

Cytosolic and mitochondrial surface factor-independent import of a synthetic peptide into mitochondria

We chemically synthesized a peptide, 11 beta-45, which was composed of 45 amino acid residues including the whole extension peptide and some of the mature portion of bovine cytochrome P-450(11 beta) precursor. 11 beta-45 was imported into mitochondria in vitro depending on the mitochondrial membrane potential, but its import did not require extramitochondrial ATP. Although cytosolic protein factors in the high speed supernatant of reticulocyte lysate are known to stimulate the import of various precursor proteins into mitochondria, the import of 11 beta-45 was not stimulated by cytosolic factors in reticulocyte lysate. The import of the peptide did not require mitochondrial surface protein components because its import was not affected by trypsin treatment of mitochondria. On the other hand, trypsin treatment of mitoplasts resulted in a great reduction in the import of the peptide, indicating that 11 beta-45 interacts during the import process with some protein components located inside mitochondria. These observations indicated that the peptide 11 beta-45 was imported via the potential-dependent pathway as in the case of precursor proteins, but skipped the interactions with cytosolic factors and mitochondrial surface components normally required for the import of precursor proteins.

Crystallization and preliminary X-ray study of a double-shelled spherical virus, rice dwarf virus

Rice dwarf virus (RDV) is a double-shelled spherical plant virus consisting of 46,000 Mr capsid and 114,000 Mr core proteins and minor structural proteins, and containing 12 genome segments of double-stranded RNA. The virus has been crystallized in the cubic space group I23 with a = 789 A. There are two particles per unit cell, each positioned on a point of 23 symmetry. Packing considerations showed that the diameter of the virus particle is 693 A. The crystals diffract to at least 6.5 A resolution.

Yeast gene which suppresses the defect in protein export of a secY mutant of E. coli

To find factors participating in protein translocation in yeast, we screened a yeast genomic library for genes which, when introduced into Escherichia coli, suppressed secY24, a temperature sensitive mutation of an essential integral membrane protein (SecY) required for protein export. We isolated and characterized a gene (YSY6) which improved the translocation of the OmpA protein in mutant strain IQ85(secY24). It could also suppress another mutant [rplO215(Am)], in which the level of expression of the SecY protein is decreased at high-temperature. The YSY6 gene encodes a small amphiphilic peptide consisting of 65 amino acids, which can be expressed in E. coli cells.

[A five-year follow-up study on blood pressure and serum cholesterol in junior high school children]

Blood pressure and serum cholesterol changes over a five-year period were studied in 299 junior high school children (127 males and 172 females) examined during 1980-1984 in Akita Prefecture, Japan. The six factors studied were height, weight, body mass index (by Minowa's method), systolic blood pressure, diastolic blood pressure and serum cholesterol. Mean values for systolic and diastolic blood pressure increased more than 10 mmHg during the five years in both sexes. Significant positive correlations between initial and follow-up blood pressure ('tracking') were observed. The correlation coefficients for systolic blood pressure in males and in females were 0.33 and 0.28 respectively, and those for diastolic blood pressure were 0.36 in males and 0.19 in females. While there were no significant differences in serum cholesterol levels between the two periods in either sex, the correlation coefficients, which were higher than those for blood pressure, were 0.55 in males and 0.45 in females. Among the six factors at each period, significant positive correlations were observed between height and systolic blood pressure at the initial period, and between obesity and systolic blood pressure at both periods in males and females. A significant positive relationship between obesity and serum cholesterol was seen at the follow-up period in both sexes. These data suggest that a moderate degree of 'tracking' occurs in blood pressure and serum cholesterol during childhood, and that obesity is an important factor related to blood pressure and serum cholesterol.