Mammalian male and female germ cells express a germ cell-specific Y-Box protein, MSY2

Here we report the isolation and characterization of mouse testicular cDNAs encoding the mammalian homologue of the Xenopus germ cell-specific nucleic acid-binding protein FRGY2 (mRNP3+4), hereafter designated MSY2. MSY2 is a member of the Y box multigene family of proteins; it contains the cold shock domain that is highly conserved among all Y box proteins and four basic/aromatic islands that are closely related to the other known germline Y box proteins from Xenopus, FRGY2, and goldfish, GFYP2. Msy2 undergoes alternative splicing to yield alternate N-terminal regions upstream of the cold shock domain. Although MSY2 is a member of a large family of nucleic acid-binding proteins, Southern blotting detects only a limited number of genomic DNA fragments, suggesting that Msy2 is a single copy gene. By Northern blotting and immunoblotting, MSY2 appears to be a germ cell-specific protein in the testis. Analysis of Msy2 mRNA expression in prepubertal and adult mouse testes, and in isolated populations of germ cells, reveals maximal expression in postmeiotic round spermatids, a cell type with abundant amounts of stored messenger ribonucleoproteins. In the ovary, MSY2 is present exclusively in diplotene-stage and mature oocytes. MSY2 is maternally inherited in the one-cell-stage embryo but is not detected in the late two-cell-stage embryo. This loss of MSY2 is coincident with the bulk degradation of maternal mRNAs in the two-cell embryo.

[Chemical constituents of Bufo Siccus]

OBJECTIVE

To study the chemical constituents of Bufo Siccus.

METHOD

Based on silica column chromatography six compounds were obtained from the alcoholic extract of Bufo Siccus and identified by physico-chemical and spectroscopic analyses.

RESULT

The compounds were identified as cholesterol, beta-sitosterol, resibufogenin, cinobufagin, bufalin and gamabufotalin.

CONCLUSION

Studies on the chemical constituents of Bufo Siccus were reported for the first time.

Identification of a RAPD marker linked to progressive rod-cone degeneration in dogs

Random amplified polymorphic DNA (RAPD) analysis has been used widely in plant and fungi for identification of markers linked to genetic traits and mapping, but its use is limited to identification of intra- and inter-species difference in domestic mammals. We report here identification of a RAPD-derived marker linked to progressive rod-cone degeneration (prcd), an inherited autosomal recessive retinal disease of dogs. A total of 400 standard 10-mer primers were used for amplification by use of DNA samples from normal (+/+) and affected (prcd/prcd) dogs. A single primer was identified which amplified a 1.5-kb DNA fragment only from normal dogs. PCR with longer primers designed from the sequence-characterized amplified region of the 1.5-kb DNA fragment identified a co-dominant multi-allelic polymorphism in the prcd-informative pedigree. Three recombinants were identified among 34 informative offsprings, yielding a LOD score of 5.568 at theta = 0.091. This marker was mapped to two canine-rodent hybrid cell lines in which two genes (canine homologues of human breast cancer 1 susceptibility gene, and cGMP phosphodiesterase gamma-subunit gene), and three anonymous microsatellites have been identified. This is the first reported identification of a RAPD-derived marker with multiple alleles linked to a mammalian disease locus.

The aroQ and pheA domains of the bifunctional P-protein from Xanthomonas campestris in a context of genomic comparison

The gene (denoted aroQp.pheA) encoding the bifunctional P-protein (chorismate mutase-P/prephenate dehydratase) from Xanthomonas campestris was cloned. aroQp.pheA is essential for L-phenylalanine biosynthesis. DNA sequencing of the smallest subclone capable of functional complementation of an Escherichia coli phenylalanine auxotroph revealed a putative open reading frame (ORF) of 1200 bp that would encode a 43,438-Da protein. AroQp.PheA exhibited 51% amino acid identity with a Pseudomonas stutzeri homologoue and greater than 30% identities with AroQp.PheA proteins from Haemophilus influenzae, Neisseria gonorrhoeae, and a number of enteric bacteria. AroQp.PheA from X. campestris, when expressed in E. coli, possesses a 40-residue amino-terminal extension that is lysine-rich and that is absent in all of the AroQp.PheA homologues known at present. About 95% of AroQp.PheA was particulate and readily sedimented by low-speed centrifugation. Soluble preparations of cloned AroQp.PheA exhibited a native molecular mass of 81,000 Da, indicating that the active enzyme species is a homodimer. These preparations were unstable after purification of about 40-fold, even in the presence of glycerol, which was an effective protectant before fractionation. When AroQp.PheA was overproduced by a T7 translation vector, unusual inclusion bodies having a macromolecular structure consisting of protein fibrils were observed by electron microscopy. Insoluble protein collected at low-speed centrifugation possessed high catalytic activity. The single band obtained via SDS-PAGE was used to confirm the translational start via N-terminal amino acid sequencing. A perspective on the evolutionary relationships of monofunctional AroQ and PheA proteins and the AroQp.PheA family of proteins is presented. A serC gene located immediately upstream of X. campestris aroQp.pheA appears to reflect a conserved gene organization, and both may belong to a single transcriptional unit.

[Pharmacological studies of shundao granules on gastrointestinal track]

The traditional Chinese medicine Shundao Granules po markedly inhibited the formation of gastric ulcers induced by indomethacin, restraint and pyloric ligatin in rats. A decreased volume of gastric juice collected from pyloric ligated stomaches and a reduced level of gastric acid have been observed. The results showed that Shundao Granules had markedly analgesic action and significantly enhanced intestinal movement in mice, increased propulsive rate of small ingestion in mice.

Oxidation of cysteamine induced by gas-phase radicals from combustion smoke of poly (methyl methacrylate)

In order to obtain fundamental knowledge on biological damage caused by the smoke from combustion of poly(methyl-methacrylate) (PMMA), we investigated the oxidation of cysteamine induced by PMMA smoke. We suggest that the long-lived and oxygen-centered radicals involved in PMMA smoke should play an important role in the oxidation of cysteamine. The mechanism for the oxidation of cysteamine by combustion smoke of PMMA was postulated as radical initiated chain reactions, taking into account the effect of pH, oxygen and radical concentrations.

[Resection of small primary liver cancer: clinical analysis of 82 cases]

OBJECTIVE

To determine which clinicopathologic features and surgical modalities are related to the prognosis of small primary liver cancer (SPLC).

METHOD

Eighty-two patients who had under gone operations for SPLC (<or= 5.0 cm in diameter) from 1988 to 1995 were retrospectively studied. 60 patients were HBsAg positive, and 71 patients suffered from liver cirrhosis. Bisegmentectomy, segmentectomy and partial resections were performed in 13, 14 and 55 patients separately.

RESULT

The overall operative mortality was 1.2%, and the 1-, 3-, 5-year survival rates were 92.7%, 72.5% and 54.3%, respectively. The 5-year survival rates of 78 patients with hepatocellular carcinoma according to histologic features were 79.6%, 49.9% and 41.1% in well-differentiated (15 patients), moderately (53), and poorly differentiated (10) groups. Recurrence and metastasis rates in 1, 3, 5 years were 12.8%, 40.7% and 71.5%, separately.

CONCLUSION

SPLC has the same history of large PLC. Early diagnosis and limited hepatic resection are very important to decrease the mortality and increase the survival rate.

[Association between angiotensin II type I receptor gene and human essential hypertension]

OBJECTIVE

To determine whether the angiotensin II type I receptor gene might be implicated in human essential hypertension.

METHODS

This was a case-control study on hypertension and normal blood pressure in Chinese DNA abstracted samples from 51 cases of essential hypertension and 74 normal controls were analysed by polymerase chain reaction,digestion of restriction enzyme and electrophesis.

RESULTS

The genotype frequency of 1166A/1166C was 0. 196 (10/51) in the essential hypertension group, 0.081 (6/74) in the control group. The genotype frequency of 1166C/1166C was 0 in both groups. The gene frequency of 1166C was 0.098 in the essential hypertension group, 0.041 in the controls. There was a significant increase in allelic frequency of 1166C in hypertension.

CONCLUSION

The results indicate that the increase in allelic frequency of 1166C is a risk factor and hence suggest that the change in the angiotensin II type I receptor gene is associated with essential hypertension.

ESA1 is a histone acetyltransferase that is essential for growth in yeast

Posttranslational acetylation of core histone amino termini has long been associated with transcriptionally active chromatin. Recent reports have demonstrated histone acetyltransferase activity in a small group of conserved transcriptional regulators directly linked to gene activation. In addition, the presence of a putative acetyltransferase domain has been discovered in a group of proteins known as the MYST family (for its founding members MOZ, YBF2/SAS3, SAS2, and Tip60). Members of this family are implicated in acute myeloid leukemia (MOZ), transcriptional silencing in yeast (SAS2 and YBF2/SAS3), HIV Tat interaction in humans (Tip60), and dosage compensation in Drosophila (MOF). In this report, we express a yeast ORF with homology to MYST family members and show it possesses histone acetyltransferase activity. Unlike the other MYST family members in Saccharomyces cerevisiae this gene is essential for growth.

Linkage analysis and comparative mapping of canine progressive rod-cone degeneration (prcd) establishes potential locus homology with retinitis pigmentosa (RP17) in humans

Progressive rod-cone degeneration (prcd) is the most widespread hereditary retinal disease leading to blindness in dogs and phenotypically is the canine counterpart of retinitis pigmentosa (RP) in humans. In previous efforts to identify the genetic locus for prcd, the canine homologs for many of the genes causally associated with RP in humans, such as RHO, PDE6B, and RDS/peripherin, have been excluded. In parallel with a recent undertaking to establish a framework map of the canine genome, multiple prcd-informative pedigrees have been typed with a panel of more than 100 anchor loci and microsatellite-based markers. Identification of a linkage group flanking prcd ([TK1, GALK1, prcd]-[MYL4, C09.173, C09.2263]-RARA-C09.250-C09.474-NF1) localizes prcd close to the centromeric end of canine chromosome 9 (CFA9), and excludes RARA as a candidate gene. The conserved synteny of this region of CFA9 and distal human chromosome 17q establishes the potential locus homology of prcd in the dog with RP17, a human retinitis pigmentosa locus for which no gene has yet been identified. Assignment of the prcd disease locus to an identified canine autosome represents a powerful application of the developing canine linkage map in medical genetics. The usefulness of this approach is further demonstrated by identification of the correspondence of the prcd interval to homologous human and mouse chromosomal regions. The rapid progress that is now occurring in the field of canine genetics will expedite the identification of the genes underlying many of the inherited traits and diseases that make the dog a unique asset for the study of mammalian traits.

The RNA- and DNA-binding protein TB-RBP is spatially and developmentally regulated during spermatogenesis

Testis brain RNA-binding protein (TB-RBP) suppresses translation in vitro and attaches mRNAs to microtubules by binding to conserved elements in the 3' untranslated regions (UTRs) of specific testis and brain mRNAs. Purification of TB-RBP from testicular and brain cytoplasmic extracts has revealed that mouse TB-RBP is 99% identical to the human protein translin, a recombination "hot spot" binding protein associated with chromosomal translocations. Using a cDNA encoding TB-RBP, the gene copy number and the developmental expression of TB-RBP have been analyzed by Southern blotting, Northern blotting, and in situ hybridization. In the mouse, TB-RBP is encoded by a single copy gene. In mouse testes, three TB-RBP mRNAs of about 1.2, 1.7, and 3.0 kb are developmentally regulated with high levels of expression in meiotic and postmeiotic germ cells. A fourth TB-RBP transcript of about 3.2 kb is seen in the brain. In situ hybridization confirms high levels of testicular TB-RBP mRNAs in meiotic and postmeiotic cells, with the highest levels of TB-RBP mRNAs in pachytene spermatocytes and round spermatids of the mouse and in round spermatids of the rat. RNase H digestion assays reveal that the three TB-RBP mRNAs of mouse testes result from processing differences in their 3' untranslated regions. These data demonstrate that multiple TB-RBP mRNAs are primarily expressed in meiotic and postmeiotic germ cells in the mammalian testis, and although the specific RNA-binding ability of TB-RBP appears limited to brain and testis, TB-RBP mRNAs are widely expressed.

[Investigation of fluorescence spectra of alum floc]

The sharp fluorescence peak of alum floc was observed at 340nm. The peak height at 340nm is in proportion to alum concentration under same degree of neutralization. There is similar regular change of this peak height as change of neutralization degree under different alum concentration.

Complete deletion of factor IX gene and inhibition of factor IX activity in a labrador retriever with hemophilia B

Hemophilia B is a heritable bleeding disorder caused by mutations in the gene coding for coagulation factor IX. The defect has been identified in purebred and mixed-breed dogs. Management of affected dogs requires transfusion of canine blood products supplying active factor IX. Production of inhibitors to factor IX is a complication of transfusion therapy that has been documented as affecting human patients. Risk for producing coagulation inhibitors is greatest for patients having large factor IX gene deletions. To our knowledge, this is the first report of canine factor IX inhibitor production in dogs. The affected dog had clinically severe hemophilia B caused by complete deletion of the factor IX gene and developed resistance to transfusion. Comprehensive evaluation of hemophilic dogs, including assays of specific factor activity, concentration, and factor inhibition, enhances diagnosis and management of this bleeding disorder. Characterization of the molecular defect causing hemophilia is useful for genetic counseling and identifying individuals at highest risk for producing coagulation inhibitors.

Activation of p53 sequence-specific DNA binding by acetylation of the p53 C-terminal domain

The tumor suppressor p53 exerts antiproliferation effects through its ability to function as a sequence-specific DNA-binding transcription factor. Here, we demonstrate that p53 can be modified by acetylation both in vivo and in vitro. Remarkably, the site of p53 that is acetylated by its coactivator, p300, resides in a C-terminal domain known to be critical for the regulation of p53 DNA binding. Furthermore, the acetylation of p53 can dramatically stimulate its sequence-specific DNA-binding activity, possibly as a result of an acetylation-induced conformational change. These observations clearly indicate a novel pathway for p53 activation and, importantly, provide an example of an acetylation-mediated change in the function of a nonhistone regulatory protein. These results have significant implications regarding the molecular mechanisms of various acetyltransferase-containing transcriptional coactivators whose primary targets have been presumed to be histones.

Synergistic activation of transcription by CBP and p53

The tumour suppressor p53 is a transcriptional regulator whose ability to inhibit cell growth is dependent upon its transactivation function. Here we demonstrate that the transcription factor CBP, which is also implicated in cell proliferation and differentiation, acts as a p53 coactivator and potentiates its transcriptional activity. The amino-terminal activation domain of p53 interacts with the carboxy-terminal portion of the CBP protein both in vitro and in vivo. In transfected SaoS-2 cells, CBP potentiates activation of the mdm-2 gene by p53 and, reciprocally, p53 potentiates activation of a Gal4-responsive target gene by a Gal4(1-147)-CBP(1678-2441) fusion protein. A double point mutation that destroys the transactivation function of p53 also abolishes its binding to CBP and its synergistic function with CBP. The ability of p53 to interact physically and functionally with a coactivator (CBP) that has histone acetyltransferase activity and with components (TAFs) of the general transcription machinery indicates that it may have different functions in a multistep activation pathway.

The RNA-binding protein, TB-RBP, is the mouse homologue of translin, a recombination protein associated with chromosomal translocations

The mouse RNA-binding protein, TB-RBP, suppresses translation in vitro and attaches mRNAs to microtubules by binding to conserved elements in the 3' untranslated regions of specific mRNAs. We have now purified TB-RBP from testicular and brain cytoplasmic extracts and cloned its cDNA. We find that the mouse TB-RBP cDNAs contain an open reading frame of 228 amino acids with a leucine zipper domain within its C terminus, a transmembrane helix, and a group of putative phosphorylation sites. TB-RBP shows 99% identity to the human protein, translin, a recombination hotspot-binding protein associated with chromosomal translocations [Aoki, K., Suzuki, K., Sugano, T., Tasaka, T., Nakahara, K., Kuge, O., Omori, A. & Kasai, M. (1995) Nat. Genet. 10, 167-174]. As shown for translin, TB-RBP also binds to single-stranded DNAs containing a broad range of consensus sequences, many of which are similar to the Y and H RNA-binding sequences. Recombinant TB-RBP was synthesized and an antiserum was prepared against the recombinant protein. The identity between translin and TB-RBP was confirmed by demonstrating that immunoprecipitation of TB-RBP from testicular extracts abolished formation of the RNA-TB-RBP complex. Based upon its DNA binding to target sequences in clustered breakpoint regions, we propose that TB-RBP may be involved in DNA recombination or DNA repair in male germ cells.

The enzymatic activity of Cu/Zn superoxide dismutase does not fluctuate in mouse spermatogenic cells despite mRNA changes

In the mammalian testis, multiple mRNAs encoding the copper zinc superoxide dismutase (SOD-1) are expressed in postmeiotic male germ cells. Here we relate SOD-1 mRNA levels to SOD-1 protein and enzyme activity levels in mouse spermatogenic cells. Although the sizes and relative amounts of the multiple SOD-1 mRNAs vary as male germ cells enter meiosis and proceed into the postmeiotic stages of spermatogenesis, the amount of SOD-1 protein and enzyme activity does not fluctuate significantly, suggesting a precise control of SOD-1 activity in male germ cells.

Sertoli cells in culture and mRNA differential display provide a sensitive early warning assay system to detect changes induced by xenobiotics

We have used cultured rat Sertoli cells as an "early warning system" to monitor for morphological and biochemical changes induced by two different xenobiotics-cadmium acetate and polychlorinated biphenyls (PCBs). Sertoli cells begin to round, become vacuolized, and detach from their substrate within 24 hours of culture in the presence of cadmium at concentrations of 0.5-1.0 microM. Similar results were obtained with a lower dose of cadmium (0.01 microM) after 72 hours. When Sertoli cells are cultured for 24 hours in the presence of a mixture of PCBs (3,3',4,4'-tetrachlorobiphenyl, 2,2',4,6,6'-pentachlorophenyl, and 2,2',3,3',4,5,5', 6,6'-nonachlorobiphenyl) at concentrations of 1.0-2.0 microM, they enlarge. After 72 hours, a lower dose of PCBs (0.01 microM) produces similar cellular enlargement. Despite their changes in morphology, no reduction in Sertoli cell viability was seen at any of the concentrations or time points studied for either toxicant. Using mRNA differential display, a number of novel cDNAs were detected when cells were cultured with either cadmium or the PCBs, demonstrating that changes in gene expression accompany the changes in Sertoli cell structure. We propose that Sertoli cells in culture and mRNA differential display provide a sensitive morphological and biochemical assay system to detect early direct effects of low concentrations of toxicants on mammalian Sertoli cells.

L-Arogenate Is a Chemoattractant Which Can Be Utilized as the Sole Source of Carbon and Nitrogen by Pseudomonas aeruginosa

L-Arogenate is a commonplace amino acid in nature in consideration of its role as a ubiquitous precursor of L-phenylalanine and/or L-tyrosine. However, the questions of whether it serves as a chemoattractant molecule and whether it can serve as a substrate for catabolism have never been studied. We found that Pseudomonas aeruginosa recognizes L-arogenate as a chemoattractant molecule which can be utilized as a source of both carbon and nitrogen. Mutants lacking expression of either cyclohexadienyl dehydratase or phenylalanine hydroxylase exhibited highly reduced growth rates when utilizing L-arogenate as a nitrogen source. Utilization of L-arogenate as a source of either carbon or nitrogen was dependent upon (sigma)(sup54), as revealed by the use of an rpoN null mutant. The evidence suggests that catabolism of L-arogenate proceeds via alternative pathways which converge at 4-hydroxyphenylpyruvate. In one pathway, prephenate formed in the periplasm by deamination of L-arogenate is converted to 4-hydroxyphenylpyruvate by cyclohexadienyl dehydrogenase. The second route depends upon the sequential action of periplasmic cyclohexadienyl dehydratase, phenylalanine hydroxylase, and aromatic aminotransferase.

Targeted disruption of the melanocortin-4 receptor results in obesity in mice

The melanocortin-4 receptor (MC4-R) is a G protein-coupled, seven-transmembrane receptor expressed in the brain. Inactivation of this receptor by gene targeting results in mice that develop a maturity onset obesity syndrome associated with hyperphagia, hyperinsulinemia, and hyperglycemia. This syndrome recapitulates several of the characteristic features of the agouti obesity syndrome, which results from ectopic expression of agouti protein, a pigmentation factor normally expressed in the skin. Our data identify a novel signaling pathway in the mouse for body weight regulation and support a model in which the primary mechanism by which agouti induces obesity is chronic antagonism of the MC4-R.

Two contact regions between Stat1 and CBP/p300 in interferon gamma signaling

Interferon gamma (IFN-gamma) induces rapid tyrosine phosphorylation of the latent cytoplasmic transcription factor, Stat1, which then forms homodimers, translocates to the nucleus and participates in IFN-gamma-induced transcription. However, little is known of the interactions between Stat1 and the general transcription machinery during transcriptional activation. We show here that Stat1 can directly interact with the CREB-binding protein (CBP)/p300 family of transcriptional coactivators. Specifically, two interaction regions were identified: the amino-terminal region of Stat1 interacts with the CREB-binding domain of CBP/p300 and the carboxyl-terminal region of Stat1 interacts with the domain of CBP/p300 that binds adenovirus E1A protein. Transfection experiments suggest a role for these interactions in IFN-gamma-induced transcription. Because CBP/p300-binding is required for the adenovirus E1A protein to regulate transcription of many genes during viral replication and cellular transformation, it is possible that the anti-viral effect of IFN-gamma is based at least in part on direct competition by nuclear Stat1 with E1A for CBP/p300 binding.

[A study on combination therapy of Western and traditional Chinese medicine of acute viral myocarditis]

To investigate the combination therapy of Western and traditional Chinese medicine on treatment of acute viral myocarditis, 48 patients were randomly divided into 2 groups. The 1st group consisted of 30 patients, receiving the combination therapy of Western and traditional Chinese medicine, including Astragalus membranaceus, taurine, coenzyme Q10 and antiarrhythmics, while the 2nd group consisted of 18 patients, receiving the conventional therapy, including glucose-insulin-potassium (GIK), coenzyme Q10 and also antiarrhythmics.

RESULTS

The efficacy of combination therapy of western and traditional Chinese medicine was better than that of conventional therapy in improving the clinical manifestation, negative converting positive EVsRNA in peripheral leukocytes and controlling the premature beats.

CONCLUSION

The combination therapy of western and traditional Chinese medicine was an effective method in treating acute viral myocarditis.

[Regional brain calcium change in rabbit cerebral ischemia]

OBJECTIVE

To study whether regional brain calcium change would be an important factor for ischemic neuranal damage and whether calcium antagonist would exert protective effects on cerebral ischemia.

METHODS

OCPC autoanalyzer method, was used to measure the regional brain calcium and observe the influence of flunarizine (FNZ) 48 hours after the rabbit middle cerebral artery occlusion (MCAO).

RESULTS

48 hours after MCAO, the calcium in the ischemic middle cerebral artery territory was 10.8 times as much as that in the pseudo-occluded controls, and FNZ could significantly decrease the ischemic brain calcium (P < 0.05) and the ischemic cerebral edema (P < 0.01).

CONCLUSION

Caoverload was animportant factor leading to ischemic neuronal death, and FNZ has protective effects on cerebral ischemia.

Translation of a testis-specific Cu/Zn superoxide dismutase (SOD-1) mRNA is regulated by a 65-kilodalton protein which binds to its 5' untranslated region

Mouse testes contain two distinct superoxide dismutase (SOD-1) transcripts which differ by 114 nucleotides in their 5' untranslated regions (UTRs) (W. Gu, C. Morales, and N. B. Hecht, J. Biol. Chem. 270:236-243, 1995). The shorter SOD-1 mRNA, a somatic type SOD-I mRNA (SSOD-1), is ubiquitously expressed in all somatic tissues as well as in testes. The larger SOD-1 mRNA, a testis-specific SOD-1 mRNA (TSOD-1), derived from an alternative upstream start site, is transcribed solely in postmeiotic germ cells and is translationally regulated during spermiogenesis. Since the two mRNAs have identical nucleotides except that TSOD-1 has an additional sequence at its 5' terminus, we have proposed that the extra 5' UTR sequence may be involved in the translational control of the TSOD-1 mRNA during spermiogenesis. Here we show that, when assayed in a cell-free system, TSOD-1 is translated only slightly less efficiently than SSOD-1. RNA gel retardation and UV cross-linking assays reveal that a testicular cytoplasmic protein (Cu/Zn superoxide dismutase RNA-binding protein [SOD-RBP]) of about 65 kDa specifically binds to the extended 5' UTR of TSOD-1. After purification of SOD-RBP by RNA affinity chromatography, we demonstrate that SOD-RBP can repress the in vitro translation of TSOD-1 mRNA but not SSOD-1 mRNA or cotranslated luciferase mRNA. We conclude that SOD-RBP serves as a repressor in the translation of TSOD-1 mRNA during spermiogenesis and thereby fine-tunes the level of Cu/Zn superoxide dismutase produced in maturing germ cells.

Increased accommodation of nascent RNA in a product site on RNA polymerase II during arrest

RNA polymerases encounter specific DNA sites at which RNA chain elongation takes place in the absence of enzyme translocation in a process called discontinuous elongation. For RNA polymerase II, at least some of these sequences also provoke transcriptional arrest where renewed RNA polymerization requires elongation factor SII. Recent elongation models suggest the occupancy of a site within RNA polymerase that accommodates nascent RNA during discontinuous elongation. Here we have probed the extent of nascent RNA extruded from RNA polymerase II as it approaches, encounters, and departs an arrest site. Just upstream of an arrest site, 17-19 nucleotides of the RNA 3'-end are protected from exhaustive digestion by exogenous ribonuclease probes. As RNA is elongated to the arrest site, the enzyme does not translocate and the protected RNA becomes correspondingly larger, up to 27 nucleotides in length. After the enzyme passes the arrest site, the protected RNA is again the 18-nucleotide species typical of an elongation-competent complex. These findings identify an extended RNA product groove in arrested RNA polymerase II that is probably identical to that emptied during SII-activated RNA cleavage, a process required for the resumption of elongation. Unlike Escherichia coli RNA polymerase at a terminator, arrested RNA polymerase II does not release its RNA but can reestablish the normal elongation mode downstream of an arrest site. Discontinuous elongation probably represents a structural change that precedes, but may not be sufficient for, arrest by RNA polymerase II.

Molecular cloning of mouse somatic and testis-specific H2B histone genes containing a methylated CpG island

We have isolated a mouse testis-specific H2B histone gene based on the unusual methylation of the CpG island of rat testis-specific H2B gene in somatic tissues. After digestion of genomic DNA with the methylation-sensitive restriction enzyme Hha I, we found that, among 10-20 copies of mouse H2B histone genes, at least three copies are methylated in somatic tissues, but not in testis. Cloning and sequence analysis of two methylated H2B genes revealed that one gene, MTH2B, is strikingly similar to the testis-specific histone H2B (TH2B) gene of rat and the other, psH2B, is a pseudogene of the somatic-type H2B gene. Northern blot analysis revealed that the expression of the MTH2B gene is testis-specific. During spermatogenesis, the MTH2B gene is expressed predominantly in pachytene spermatocytes, as observed in the expression of rat TH2B gene. Interestingly, the MTH2B gene is largely unmethylated in embryonic stem cells, but methylated in F9 embryonal carcinoma cells. The psH2B pseudogene is methylated in somatic tissues and F9 cells, but only partially methylated in embryonic stem cells. Methylation of the psH2B pseudogene seems to be attributed to its location within the context of repetitive sequences including the B1 element. The unmethylation of both H2B histone genes in the testis explains how CpG islands of those histone genes can be maintained during evolution despite heavy methylation in somatic tissues.

In postmeiotic male germ cells poly (A) shortening accompanies translation of mRNA encoding gamma enteric actin but not cytoplasmic beta and gamma actin mRNAs

In the mammalian testis the cytoplasmic beta and gamma actins are expressed in all stages of germ-cell differentiation, whereas gamma enteric actin is expressed in germ cells solely in postmeiotic stages. Northern blot analysis of mouse testicular RNAs reveals actin mRNAs of about 2.1, 1.5, and 1.4 kB. The 2.1-kB mRNAs encode the cytoplasmic beta and gamma actins, whereas the two faster-migrating actin mRNAs encode gamma enteric actin. When postmitochondrial mouse testis extracts are fractionated by sucrose gradient centrifugation, the 1.5-kB gamma enteric actin mRNA is primarily found in the nonpolysomal fraction, whereas the 1.4-kB gamma enteric actin is polysomal. When the poly (A) tails are removed, the nonpolysomal and polysomal gamma enteric actin mRNAs both migrate at 1.3 kB, indicating that the difference in electrophoretic mobilities of the two gamma enteric actin mRNAs is caused by poly (A) length differences. The nonpolysomal and polysomal forms of the cytoplasmic beta and gamma actins show similar electrophoretic mobilities before and after deadenylation. Sequence comparison of the 3' untranslated region of the mouse gamma enteric actin to the 3' untranslated regions of other testicular mRNAs that undergo partial deadenylation reveals three highly-conserved sequence elements. These data demonstrate that the poly (A) shortening of polysomal mRNAs previously seen only with testis-specific mRNAs that are stored as mRNPs also occurs with mRNAs of widely-expressed genes that are expressed in postmeiotic male germ cells. The mRNAs all contain specific conserved sequence elements in their 3' untranslated regions.

Developmental expression of glutathione peroxidase, catalase, and manganese superoxide dismutase mRNAs during spermatogenesis in the mouse

We have examined in mouse testis the steady-state levels of mRNAs encoding glutathione peroxidase (GSHPx), catalase (CAT), and superoxide dismutase 2 (SOD-2), three enzymes essential for the antioxidant protection of cells. In RNA preparations derived from prepuberal and adult testes and from isolated populations of meiotic and post-meiotic germ cells, one major GSHPx mRNA of about 0.8 kilobases (kb) and one major CAT mRNA of about 2.4 kb were detected. Three SOD-2 mRNAs of about 2.2, 1.2, and 1.0 kb were found in testis. In contrast to GSHPx and CAT, the mRNA levels of SOD-2 were higher in testis than in liver. SOD-2 mRNA levels are developmentally and translationally regulated with maximal levels of expression in early post-meiotic germ cells, whereas the levels of GSHPx and CAT mRNAs are relatively constant in both prepuberal and adult testes. These data suggest that translational regulation plays a more prominent role for SOD-2 expression than for GSHPx or CAT expression in the mammalian testis.

Understanding water: molecular dynamics simulations of myoglobin

Molecular dynamics simulations were performed on CO myoglobin to evaluate the stability of the bound water molecules as determined in a neutron diffraction analysis. The myoglobin structure derived from the neutron analysis provided the starting coordinate set used in the simulation. The simulations show that only a few water molecules are tightly bound to protein atoms, while most solvent molecules are labile, breaking and reforming hydrogen bonds. Comparison between myoglobin in solution and in a single crystal highlighted some of the packing effects on the solvent structure and shows that water solvent plays an indispensable role in protein dynamics and structural stability. The described observations explain some of the differences in the experimental results of protein hydration as observed in NMR, neutron and X-ray diffraction studies.

Variation in the size of nascent RNA cleavage products as a function of transcript length and elongation competence

RNA polymerase II arrested at specific template locations can be rescued by elongation factor SII via RNA cleavage. The size of the products removed from the 3'-end of the RNA varies. The release of single nucleotides, dinucleotides, and larger oligonucleotides has been detected by different workers. Dinucleotides tend to originate from SII-independent complexes and 7-14 base products from SII-dependent complexes (Izban, M. G., and Luse, D. S. (1993) J. Biol. Chem. 268, 12874-12885). Different modes of cleavage have also been recognized for bacterial transcription complexes and are thought to represent important structural differences between functionally distinct transcription intermediates. Using an elongation complex "walking" technique, we have observed factor-independent complexes as they approach and become arrested at an arrest site. Dinucleotides or 7-9-base (large) oligonucleotides were released from SII-independent or dependent complexes, respectively. The abrupt shift between the release of dinucleotide versus larger products accompanied the change from factor-dependent to factor-independent elongation, as described by others. However, not all factor-independent complexes showed cleavage in dinucleotide intervals since oligonucleotides 2-6 bases long were also liberated from elongation-competent complexes. These were all 5'-coterminal oligonucleotides indicating that a preferred phosphodiester bond is targeted for cleavage in a series of related complexes. This is consistent with recent models postulating a large product binding site that can hold RNA chains whose size increases as a function of chain polymerization. A specific transitional complex was identified that acquired the ability to cleave in a large increment one base insertion event prior to attaining the arrested configuration.

Testis-brain RNA-binding protein, a testicular translational regulatory RNA-binding protein, is present in the brain and binds to the 3' untranslated regions of transported brain mRNAs

Previous studies have demonstrated that a phosphoprotein in testis binds to transcript c, a sequence containing two highly conserved elements, Y and H, in the 3' untranslated region (UTR) of mouse protamine 2 mRNA (mP2) and represses its translation in vitro. When gel-retardation assays were performed with cytoplasmic extracts prepared from seven different mouse tissues, we found that brain in addition to testis contains a protein that binds to transcript c. Both the testis and brain proteins are found exclusively in the nonpolysomal fractions of their postmitochondrial extracts. The testis and brain proteins appear to be identical according to numerous criteria: the complexes they form with transcript c have identical mobility in native gels, identical optimal pH, identical lability to increased salt concentrations, identical chromatographic properties, identical molecular sizes as judged from UV crosslinking, and identical peptide mapping as revealed by V8 digestion of the UV crosslinked protein-RNA complexes. In addition to binding to the same conserved sequence in the 3'UTR of mP2, the phosphoprotein from testis and brain, hereafter called testis-brain RNA-binding protein (TB-RBP), also specifically binds to a similar sequence in the 3'UTR of brain Tau mRNA. Since TB-RBP binds to the 3'UTRs of several translationally regulated mRNAs in testis and since numerous transported brain mRNAs also contain the same conserved binding elements, we propose that TB-RBP plays a role in mRNA storage, translocation, and/or localization in brain and testis.

Multiple Tandemly Repeated Binding Sites for the YY1 Repressor and Transcription Factors AP-1 and SP-1 Are Clustered within Intron-1 of the Gene Encoding the IE110 Transactivator of Herpes simplex Virus Type 1

Expression of the IE110 (ICP0) transactivator protein of HSV appears to be critical for reactivation from the latent state and occurs at immediate-early times during the lytic cycle under the control of an upstream divergent enhancer-promoter region that contains multiple Oct and Sp-1 binding sites overlapping with VP16 response elements. Surprisingly, the large 800-bp first intron of the HSV-1 IE110 gene also proved to have a complex repetitive organization encompassing multiple transcription factor binding sites within four distinct domains. DNaseI footprinting studies revealed that 13 of 17 copies of a 15-bp repeated element represented high-affinity binding sites for the cellular YY1 repressor protein. Between 4 and 7 of these sites are direct tandem repeats and the rest are interpersed with three repeated AT-rich motifs and a dyad symmetry region containing two strong AP-1 binding sites and an adjacent SP-1 binding site on each arm. Several of the YY1 sites also bound weakly to SRF. The intron also contains four clustered purine/pyrimidine tracts of between 16 and 23 bp long. Both the AP-1/AP-2/SP-1 dyad protein binding region and, to a lesser extent, the YY1 tandem-repeat cluster conferred responsiveness to TPA when placed upstream of a heterologous promoter in transient expression assays. The functional significance of the HSV-1 IE110 intron region is unknown as yet, but the novel arrangement of tandemly repeated YY1 sites has the potential to produce structural bending and transcriptional attenuation effects. Interestingly, few of these transcription factor binding motifs are conserved in the equivalent IE110 intron of HSV-2, and the domain appears to represent a unique alternative control region that is specific for HSV-1. Copyright 1995 S. Karger AG, Basel

Identification of a decay in transcription potential that results in elongation factor dependence of RNA polymerase II

The rate of RNA elongation by RNA polymerase II (pol II) is affected by DNA sequences called intrinsic arrest sites. Efficient transcription through these sites requires elongation factor SII. In addition to the sequence-specific features of the DNA, we show that the acquisition of SII-dependence is a function of its "dwell-time" at an arrest site. This temperature-dependent decay in elongation potential appears irreversible, implying that factor-dependent and factor-independent elongation complexes are not mutually interconvertible at this position. TFIIF and NH4Cl are known to increase the elongation rate of pol II. Both agents preempt arrest, consistent with the idea that elongation dwell time influences the process. TFIIF and SII act upon different steps in a complementary way to prevent or resolve arrest, respectively. They are probably instrumental in facilitating the efficient transcription of large eukaryotic genes in vivo.

Molecular dynamics simulation of hydration in myoglobin

This study was carried out to evaluate the stability of the 89 bound water molecules that were observed in the neutron diffraction study of CO myoglobin. The myoglobin structure derived from the neutron analysis was used as the starting point in the molecular dynamics simulation using the software package CHARMM. After solvation of the protein, energy minimization and equilibration of the system, 50 ps of Newtonian dynamics was performed. This data showed that only 4 water molecules are continuously bound during the length of this simulation while the other solvent molecules exhibit considerable mobility and are breaking and reforming hydrogen bonds with the protein. At any instant during the simulation, 73 of the hydration sites observed in the neutron structure are occupied by water.

Molecular cardiomyoplasty: potential cardiac gene therapy for chronic heart failure

In this study, we evaluated the feasibility of converting cardiac fibroblasts into skeletal muscle cells by forced expression of the MyoD gene, one of the basic helix-loop-helix myogenic factors. Primary cardiac fibroblasts, isolated from newborn rats, were infected with retrovirus-carrying sense or antisense MyoD gene. Ten days after infection, expression of MyoD protein was demonstrated in 95% of cells infected with sense MyoD virus by intense nuclear immunostaining with a MyoD polyclonal antibody. In contrast, none of the cells infected with antisense MyoD virus showed staining. On withdrawal of serum, 95% of MyoD positive cells became elongated and, in the presence of appropriate cell density, fused to form multinucleated myotubes, morphologically similar to striated muscle cell. Expression of downstream myogenic differentiation markers, myosin heavy chain and myocyte-specific enhancer factor 2, in 95% of these myotubes were detected by intense cytoplasmic and nuclear immunostaining, respectively, with specific antibodies. In contrast, no detectable staining was noted in MyoD negative cells. Spontaneous contractile movements were noted in a few clusters of myotubes. In summary, cardiac fibroblasts were able to be converted into bonafide potentially functional skeletal myocytes as shown by definitive morphologic and biochemical changes. Further studies with in vivo models are needed to explore this unique molecular strategy to treat patients with chronic heart failure.

Cardiac myocyte terminal differentiation. Potential for cardiac regeneration

The exact mechanism of terminal differentiation in cardiac myocytes is currently unknown. Studies in the skeletal muscle system provided a model where muscle lineage termination gene directly interacts with Rb to produce and maintain the terminally differentiated state. This interaction provided the critical components for the lock in cell cycle arrest in skeletal muscle cell. Cardiac muscle appears on the surface very similar to skeletal muscle especially since they share large numbers of structural and contractile proteins. However, it is clear that cardiac muscle cells are distinct biologically at the regulatory level. First and foremost, differentiation and capacity for hyperplasia (mitosis) is not mutually exclusive, in that the heart being the first functional organ embryologically is able to grow via cell division until shortly after birth. Thereafter further growth is provided by hypertrophy. In skeletal muscle, these two processes, differentiation and ability to undergo mitosis, appear to be mutually exclusive. Second, cardiac muscles have not been shown to express any of the skeletal muscle determination basic helix loop helix factors like myoD or any proteins that are functionally similar. Third, heterokaryons of cardiac myocytes and fibroblasts reveal a lack of dominance of the cardiac muscle phenotype. This is distinctly different in skeletal muscle, whose phenotype is dominant which provided a platform to identify the skeletal muscle determination gene, myoD. Although various basic helix loop helix proteins and homeobox genes have been identified in cardiac myocytes, their function remains to be elucidated. At this time no cardiac determination gene has been identified. Despite these differences, we have shown that the biology of pocket proteins Rb and P107 is similar in skeletal and cardiac myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Poly (A) binding protein is bound to both stored and polysomal mRNAs in the mammalian testis

RNA-binding proteins that bind to the 3' untranslated region of mRNAs play important roles in regulating gene expression. Here we examine the association between the 70 kDa poly (A) binding protein (PABP) and stored (RNP) and polysomal mRNAs during mammalian male germ cell development. PABP mRNA levels increase as germ cells enter meiosis, reaching a maximum in the early postmeiotic stages, and decreasing to a nearly nondetectable level towards the end of spermatogenesis. Most of the PABP mRNA is found in the nonpolysomal fractions of postmitochondrial extracts, suggesting that PABP mRNA is either inefficiently translated or stored as RNPs during spermatogenesis. Virtually all of the testicular PABP is bound to either polysomal or nonpolysomal mRNAs, with little, if any, free PABP detectable. Analysis of several specific mRNAs reveals PABP is bound to both stored (RNP) and translated forms of the mRNAs. Western blot analysis and immunocytochemistry indicate PABP is widespread in the mammalian testis, with maximal amounts detected in postmeiotic round spermatids. The presence of PABP in elongating spermatids, a cell type in which PABP mRNA is nearly absent, suggests that PABP is a stable protein in the later stages of male germ cell development. The high level of testicular PABP in round spermatids and in mRNPs suggests a role for PABP in the storage as well as in the subsequent translation of developmentally regulated mRNAs in the mammalian testis.

Imidazole acetol phosphate aminotransferase in Zymomonas mobilis: molecular genetic, biochemical, and evolutionary analyses

hisH encodes imidazole acetol phosphate (IAP) aminotransferase in Zymomonas mobilis and is located immediately upstream of tyrC, a gene which codes for cyclohexadienyl dehydrogenase. A plasmid containing hisH was able to complement an Escherichia coli histidine auxotroph which lacked the homologous aminotransferase. DNA sequencing of hisH revealed an open reading frame of 1,110 bp, encoding a protein of 40,631 Da. The cloned hisH product was purified from E. coli and estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to have a molecular mass of 40,000 Da. Since the native enzyme had a molecular mass of 85,000 Da as determined by gel filtration, the active enzyme species must be a homodimer. The purified enzyme was able to transaminate aromatic amino acids and histidine in addition to histidinol phosphate. The existence of a single protein having broad substrate specificity was consistent with the constant ratio of activities obtained with different substrates following a variety of physical treatments (such as freeze-thaw, temperature inactivation, and manipulation of pyridoxal 5'-phosphate content). The purified enzyme did not require addition of pyridoxal 5'-phosphate, but dependence upon this cofactor was demonstrated following resolution of the enzyme and cofactor by hydroxylamine treatment. Kinetic data showed the classic ping-pong mechanism expected for aminotransferases. Km values of 0.17, 3.39, and 43.48 mM for histidinol phosphate, tyrosine, and phenylalanine were obtained. The gene structure around hisH-tyrC suggested an operon organization. The hisH-tyrC cluster in Z. mobilis is reminiscent of the hisH-tyrA component of a complex operon in Bacillus subtilis, which includes the tryptophan operon and aroE. Multiple alignment of all aminotransferase sequences available in the database showed that within the class I superfamily of aminotransferases, IAP aminotransferases (family I beta) are closer to the I gamma family (e.g., rat tyrosine aminotransferase) than to the I alpha family (e.g., rat aspartate aminotransferase or E. coli AspC). Signature motifs which distinguish the IAP aminotransferase family were identified in the region of the active-site lysine and in the region of the interdomain interface.

In male mouse germ cells, copper-zinc superoxide dismutase utilizes alternative promoters that produce multiple transcripts with different translation potential

Copper-zinc superoxide dismutase (SOD-1) is an enzyme that is widely expressed in eukaryotic cells and performs a vital role in protecting cells against free radical damage. In mouse testis, three different sizes of SOD-1 mRNAs of about 0.73, 0.80, and 0.93 kilobases (kb) are detected. The 0.73-kb mRNA is found in early stages of male germ cells and in all somatic tissues. The mRNAs of 0.80 and 0.93 kb are exclusively detected in post-meiotic germ cells. RNase H digestions and Northern blot analyses reveal that the three SOD-1 mRNAs are derived from two transcripts, a ubiquitously expressed transcript and a post-meiotic transcript, which differ by 114-120 nucleotides. RNase protection assays demonstrate that the additional nucleotides present in the post-meiotic mRNA are solely in the 5'-untranslated region. Using a probe derived from the 5'-untranslated region of the 0.93-kb SOD-1 mRNA, we have established that it originates from an alternative upstream promoter contiguous with the somatic SOD-1 promoter. Polysomal gradient analysis of the three mouse testis SOD-1 mRNAs reveals that the 0.93-kb SOD-1 mRNA is primarily non-polysomal, while the 0.80- and 0.73-kb SOD-1 mRNAs are mostly polysome associated. A faster migrating form of the 0.93-kb SOD-1 mRNA is present on polysomes as a result of partial deadenylation. In a cell-free translation system, the 0.73-kb SOD-1 mRNA translates about 2-fold more efficiently than the 0.93-kb SOD-1 mRNA. These data demonstrate that male germ cells transcribe two size classes of SOD-1 mRNAs with different translation potential by utilizing two different promoters, post-meiotic SOD-1 mRNAs undergo adenylation changes, and one of the post-meiotic SOD-1 mRNAs is transcribed during mid-spermiogenesis and translated days later in a partially deadenylated form.