Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q07644 (polypeptide)
 72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.
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PMID:Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation. 5 Sep 2

Poly(L-lysine), a cationic polypeptide known to undergo specific interactions with acid mucopolysaccharides, is used as a macromolecular probe in an investigation into the structure of loose connective tissue. The polypeptide apparently binds, via an electrostatic mechanism, to the mucopolysaccharide component of the tissue, leading to a reduction in the swelling of the tissue. The polypeptide does not, however, have a deswelling effect on the tissue; the ultimate reduction in swelling is influenced by the absolute amount of polybase which enters the tissue during the swelling process. Dextran 2000 is found to have a dwelling effect on the tissue which is independent of the action of the polypeptide; this is suggestive of a large degree of independence between the collagen network and the mucopolysaccharide-containing matrix. The polypeptide, moreover, causes a reduction in the excluded volume of the tissue.
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PMID:The effect of a strongly-interacting macromolecular probe on the swelling and exclusion properties of loose connective tissue. 13 77

The cytoplasm of vesicular stomatitis virus (VSV)-infected BHK cells has been separated into a fraction containing the membrane-bound polysomes and the remaining supernatant fraction. Total poly(A)-containing RNA was isolated from each fraction and purified. A 17S class of VSV mRNA was found associated almost exclusively with the membrane-bound polysomes, whereas 14,5S and 12S RNAs were found mostly in the postmembrane cytoplasmic supernatant. Poly(A)-containing VSV RNA synthesized in vitro by purified virus was resolved into the same size classes. The individual RNA fractions isolated from VSV-infected cells or synthesized in vitro were translated in cell-free extracts of wheat germ, and their polypeptide products were compared by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. The corresponding in vivo and in vitro RNA fractions qualitatively direct the synthesis of the same viral polypeptides and therefore appear to contain the same mRNA species. By tryptic peptide analysis of their translation products, the in vivo VSV mRNA species have been identified. The 17S RNA, which is compartmentalized on membrane-bound polysomes, codes for a protein of molecular weight 63,000 (P-63) which is most probably a nonglycosylated form of the viral glycoprotein, G. Of the viral RNA species present in the remaining cytoplasmic supernatant, the 14.5S RNA codes almost exclusively for the N protein, whereas the 12S RNA codes predominantly for both the NS and M proteins of the virion.
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PMID:Translation and identification of the viral mRNA species isolated from subcellular fractions of vesicular stomatitis virus-infected cells. 16 12

Poly(A)-containing RNA from rat parotid gland directs the cell-free synthesis of several products in the reticulocyte lysate translation system including a very prominent 58,000-dalton polypeptide which is immunoreactive with anti-alpha-amylase. Purified alpha-amylase has a molecular weight estimated as 56,000 daltons. The 58,000-dalton, cell-free product and alpha-amylase share common peptides as determined by analysis of their limited proteolysis digests. The cross-reactivity and peptide homology suggest that the cell-free product may be a precursor of mature alpha-amylase. While the NH2 terminus of alpha-amylase is blocked, that of the 58,000-dalton product evidently is not, and automated sequence analysis has yielded its partial sequence as: Met-X-Phe-Phe-Leu-Leu-Leu-X-Leu-Ile-X-Leu-X-X-X-X-X-X-X-X-X-Phe-X-X-X-X-X-Ile-X-X-Leu-Phe. The highly hydrophobic nature of the NH2 terminus of the 58,000-dalton, cell-free product suggests that, like other secreted polypeptides, the extra piece may play a role in the transport and secretion of the mature alpha-amylase.
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PMID:Cell-free synthesis of rat parotid preamylase. 31 Aug 17

Poly(A)-containing mRNA isolated from the islets of Langerhans obtained from two species of fish, angler fish (Lophius americanus) and sea raven (Hemitripterus americanus), stimulated protein synthesis 16-fold in a wheat germ cell-free system. Characterization of the translation products by polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed a major polypeptide weighing 11,500 daltons that was specifically precipitated by an antibody against angler fish insulin. Partial sequence analysis of the amino terminal revealed that this polypeptide is preproinsulin, in which the amino terminus of proinsulin is preceded by either 23 (angler fish) or 25 (sea raven) amino acid residues. Translation of fish islet mRNA in a wheat germ cell-free system in the presence of dog pancreas microsomal membranes led to the correct cleavage of the nascent preproinsulin, resulting in the synthesis of authentic fish proinsulin, as verified by partial sequence analysis. Moreover, the synthesized fish proinsulin was segregated, presumably into the luminal space of the dog pancreas microsomal vesicles, because it was found to be resistant to proteolysis by added trypsin and chymotrypsin. Our data thus suggest that the mechanisms and information for the transfer of secretory proteins across the microsomal membrane are highly conserved during evolution.
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PMID:Cell-free synthesis of fish preproinsulin, and processing by heterologous mammalian microsomal membranes. 32 65

The specificity of the cell-free system of Escherichia coli for mRNA was examined, and the "accessibility" of some natural and synthetic RNAs to the ribosomes was determined by measurement of AcPhe-tRNA and fMet-tRNA binding, AcPhe-puromycin and fMet-puromycin formation, and polypeptide synthesis. The E. coli system effectively initiates the translation of various synthetic RNAs with AcPhe-tRNA or fMet-tRNA under conditions optimal for the translation of viral RNA. Poly(A,G,U) is accessible to the ribosomes according to all of the above criteria. Poly(A,C,G,U), 23 S rRNA, R17 RNA, and MS2 RNA, on the other hand, show limited accessibility when tested for initiator tRNA binding, or for AcPhe-puromycin and fMet-puromycin formation. MS2 and R17 RNA, but not poly(A,C,G,U) and 23 S rRNA, show accessibility when measured by polypeptide synthesis. The results suggest that, except at initiator sites of natural mRNA, an RNA containing about equal amounts of all four bases is inaccessible to E. coli ribosomes for polypeptide synthesis. Rate constants obtained for fMet-tRNA binding with MS2 RNA, poly(A,G,U), and poly(C,G,U) indicate that the ribosomes do not have any special affinity for the viral RNA. Thus, the selection of the initiator site in protein synthesis may be critically determined more by the accessibility of the initiator codon than by ribosomal recognition of the site.
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PMID:On the accessibility and selection of the initiator site of mRNA in protein synthesis. 34 82

Polysomal RNA was extracted from human term placenta and total poly(A)-containing RNA purified by affinity chromatography on oligo(dT)-cellulose. Poly(A)-containing RNA constituted approximately 1.2% of the total polysomal RNA and 8% of this purified preparation was able to anneal with [3H]poly(U). When injected into Xenopus oocytes, this poly(A)-rich RNA directed the synthesis of a polypeptide which is immunoprecipitable with a specific antiserum to human placental lactogen. The identity of authentic human placental lactogen and the immunoreactive polypeptide synthesized in the oocytes is suggested by their identical behaviour in dodecylsulfate gel electrophoresis and by the formation of identical cyanogen bromide peptides. No precursor of human placental lactogen can be detected in the oocytes. The messenger RNA for human placental lactogen is very stable in oocytes; it is translated efficiently for a period of at least 7 days.
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PMID:Translation of biologically active messenger RNA from human placenta in Xenopus oocytes. 42 94

Poly-L-lysine (PL II; mol wt, 1000-4000) was added to fetal rat bones cultured in a chemically defined medium (BGJ) containing bovine serum albumin in the presence and absence of parathyroid hormone (PTH). Bone resorption was measured by the release of previously incorporated 45Ca. The addition of PL II at concentrations of 3-100 microgram/ml enhanced the stimulation of bone resorption by submaximal doses of PTH but had little effect on 45Ca release from control unstimulated cultures. Higher concentrations of PL II produced inhibition of 45Ca release. Dialysis of PL II did not alter enhancement or inhibition by PL II. PL II did not increase sensitivity to PTH in serum-supplemented cultures. Higher molecular weight PL II preparations were less effective. PL II did not enhance the resorptive response to 1,25-dihydroxyvitamin D, prostaglandin E2, osteoclast-activating factor, or bacterial endotoxin. The mechanism of the selective ability of PL II to enhance the response to low concentrations of PTH is unknown but may be due to the ability of this basic polypeptide to interfere with binding of PTH to sites other than the hormone receptor or to block degradation of PTH by bone.
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PMID:Enhancement of parathyroid hormone-stimulated bone resorption by poly-L-lysine. 44 5

Poly(A)-containing low molecular weight (7.5S) messenger RNA was isolated in a highly purified form from both polyribosomes and post-polysomal supernatant of rat liver mitochondria. Both mRNA's contain rather short poly(A) tracts (40-70 mononucleotides) according to a profile of their elution from poly(U)-Sepharose column with a gradient of formamide concentration. Both mRNA's when added to a preincubated mitochondrial lysate programmed the synthesis of a hydrophobic polypeptide of a molecular weight about 9000 daltons which was soluble in the neutral chloroform-methanol mixture.
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PMID:Isolation and partial characterization of poly (A)-containing 7.5S messenger RNA from rat liver mitochondria. 60 Aug 1

Poly(A)-containing RNA from polyploid uterine epithelial cells of Ascaris lumbricoides has been isolated by poly(U)-Sepharose chromatography. The bulk of poly(A)-containing RNA migrates as 18-S RNA in formamide/polyacrylamide gels. In a cell-free wheat germ system, this RNA directs the synthesis of a polypeptide with identical migration behavior in dodecylsulphate/urea/polyacrylamide gels as the polypeptide isolated from the proteinaceous eggshell. The two proteins reveal almost identical peptide patterns in fingerprint analysis. The authentic eggshell protein has been identified as a glycoprotein with a molecular weight of about 10000, as determined by dodecylsulphate/polyacrylamide gel electrophoresis. The apparent discrepancy between mRNA length and the required coding length for the protein is discussed.
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PMID:Isolation of messenger RNA coding for eggshell protein of the DNA-eliminating nematode Ascaris lumbricoides. 62 88


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