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Chloroplast ribosomal protein S7 of Chlamydomonas binds to chloroplast mRNA leader sequences and may be involved in translation initiation.

Certain mutations isolated in the 5' untranslated region (5'UTR) of the chloroplast rps7 gene in Chlamydomonas reduce expression of reporter genes. Second site suppressors in this 5'UTR sequence restore reporter expression. 5'UTR sequences with the original mutations fail to bind a 20-kD protein, one of five proteins that bind to leaders of several chloroplast genes. However, 5'UTRs from suppressed mutants restore binding to this protein but do not bind a 47-kD protein present on the wild type and the original mutant 5'UTRs. The 20-kD protein was shown to be the S7 protein of the chloroplast ribosomal small subunit encoded by rps7, whereas the 47-kD protein was shown to be RB47, a poly(A) binding protein. Our data are consistent with the hypothesis that the S7 protein plays either a general or a specific regulatory role in translation initiation in the chloroplast.

5' Untranslated Regions↗

Alterations in the protein synthetic apparatus of Friend erythroleukemia cells infected with vesicular stomatitis virus or herpes simplex virus.

We have compared the effects of infection with herpes simplex virus (HSV) and vesicular stomatitis virus (VSV) on the protein synthetic apparatus of Friend erythroleukemia cells. Previous studies demonstrated that infection with HSV rapidly shuts off the synthesis of globin and other cellular polypeptides (Y. Nischioka and S. Silverstein, 1977, Proc. Natl. Acad. Sci. U.S.A. 74: 2370-2374). In contrast to these findings, globin synthesis persists in Friend erythroleukemia cells infected with VSV. Physical measurements of the size of bulk-infected cell mRNA, using hybridization with polyuridylic acid, demonstrated that there was no detectable change in the size of mRNA's after infection with VSV. A comparison of the kinetics of hybridization of cytoplasmic RNA extracted from cells infected with either HSV or VSV with globin complementary DNA revealed that by 4 h postinfection with HSV only about 15% of the globin mRNA sequences remained, whereas there was no discernible change in the sequence abundance of globin mRNA in VSV-infected cells.

Cell Line↗

Detection of vesicular stomatitis virus RNA and its defective-interfering particles in individual mouse brains.

To develop a highly sensitive and direct assay for defective interfering (DI) particles of vesicular stomatitis virus (VSV), we reverse transcribed RNA from DI particles and cloned the DNA in pBR322 and used it as hybridization probes. At the lower limit, cDNA of about 850 nucleotides detected 150 pg of VSV RNA. For differentiation of hybridizable sequences found in the RNA of DI particles from complementary or identical sequences in the L mRNA or standard genomic RNA of VSV, RNA obtained from mouse brains was first separated by size, blotted onto nitrocellulose, and then hybridized to in vitro-labeled cDNA probe. Genomic VSV, DI, or L mRNA sequences from one-half of the brain of an infected mouse were detectable, whereas uninfected mice failed to react with this specific probe. When mice were infected intranasally with 10(8) PFU of standard VSV, most of them died between days 6 and 7, and the detection of standard genomic RNA correlated with paralysis and death. DI RNA was not detected in these mice. When mice were infected with 10(8) PFU of standard VSV together with an equivalent amount of DI particles, similar results were obtained. When fewer DI particles were inoculated together with standard virus, significant protection of mice occurred together with the detection of DI RNA. These results indicate that DI particles are protective in vivo and that the details of the virus-host interaction may resemble the cyclic growth patterns in cell cultures for standard VSV and its DI particles.

Animals↗

High-efficiency cloning of full-length cDNA.

A widely recognized difficulty of presently used methods for cDNA cloning is obtaining cDNA segments that contain the entire nucleotide sequence of the corresponding mRNA. The cloning procedure described here mitigates this shortcoming. Of the 10(5) plasmid-cDNA recombinants obtained per microgram of rabbit reticulocyte mRNA, about 10% contained a complete alpha- of beta-globin mRNA sequence, and at least 30 to 50%, but very likely more, contained the entire globin coding regions. We attribute the high efficiency of cloning full- or nearly full-length cDNA to (i) the fact that the plasmid DNA vector itself serves as the primer for first- and second-strand cDNA synthesis, (ii) the lack of any nuclease treatment of the products, and (iii) the fact that one of the steps in the procedure results in preferential cloning of recombinants with full-length cDNA's over those with truncated cDNA's.

Animals↗

RNA interference and its role in the regulation of eucaryotic gene expression.

Several years ago it was discovered that plant transformation with a transcribed sense transgene could shut down the expression of a homologous endogenous gene. Moreover, it was shown that the introduction into the cell of dsRNA (double-stranded RNA) containing nucleotide sequence complementary to an mRNA sequence causes selective degradation of the latter and thus silencing of a specific gene. This phenomenon, called RNA interference (RNAi) was demonstrated to be present in almost all eukaryotic organisms. RNAi is also capable of silencing transposons in germ line cells and fighting RNA virus infection. Enzymes involved in this process exhibit high homology across species. Some of these enzymes are involved in other cellular processes, for instance developmental timing, suggesting strong interconnections between RNAi and other metabolic pathways. RNAi is probably an ancient mechanism that evolved to protect eukaryotic cells against invasive forms of nucleic acids.

Animals↗

Changes in growth hormone (GH) messenger RNA (GH mRNA) expression in the rat anterior pituitary after single interferon (IFN) alpha administration.

INTRODUCTION: Interferon alpha (IFN-alpha) is a cytokine with pleiotropic effects which, via different pathways, influences the secretion of certain cytokines and hormones. Growth hormone (GH) secreted from the pituitary has physiological effects on various target tissues. The question is how IFN-alpha administered in various types of disease influences GH secretion. This study investigated the acute effect of IFN-alpha on GH mRNA expression in the rat anterior pituitary. OBJECTIVE: The aim of the study was to measure the cellular expression of GH mRNA by in situ hybridisation in the anterior pituitary after a single administration of IFN-alpha. MATERIAL AND METHODS: Rats were administered an intraperitoneal injection of IFN-alpha or saline. The rat pituitaries were taken 2 and 4 hours after IFN/saline administration and kept frozen until in situ hybridisation histochemistry. A 31-base(35)S-labelled oligonucleotide probe complementary to part of the exonic mRNA sequence coding for GH mRNA was used. All control and experimental sections were hybridised in the same hybridisation reaction. RESULTS: Acute administration of interferon alpha increased GH mRNA expression in the anterior pituitary in the 4-hour group in comparison with the control group, and there was no difference between the control group and the 2-hour rats. CONCLUSION: A single IFN-alpha administration was found to exert an influence on anterior pituitary GH mRNA expression. These observations may pave the way for presenting a possible new action of IFN-alpha.

Animals↗

Isolation and analysis of a rat genomic clone containing a long terminal repeat with high similarity to the oncomodulin mRNA leader sequence.

The structure of a novel long terminal repeat (LTR) from an intracisternal A particle (IAP) DNA element in the rat (Sprague-Dawley) genome was determined. This LTR has a total length of 313 base pairs (bp). Several structural features typical for retroviral LTR promoters were identified, including a "CCAAT" box, a "TATA" box, a polyadenylation signal, and a polyadenylation site. The LTR is flanked by 3-bp inverted repeats, and it consists of the three typical LTR regions, U3, R, and U5. U3 contains 213 bp, R 46 bp, and U5 54 bp, which is within the usual size range of IAP LTRs. A sequence of 60 bp in the U3 region reveals considerable similarity to a murine IAP LTR U3 element, which is known to interact with nuclear proteins. A sequence of 69 bp in the U5 and R regions has 83 and 93% similarities to an endogenous retroviral LTR from Syrian hamster and to the cDNA leader sequence of (Buffalo) rat oncomodulin, respectively. Oncomodulin is an "EF-hand" Ca2+-binding protein and appears in many human and rodent tumors and in cells with tumor-like properties but not in normal tissues. We postulate that in the rat the tumor-specific expression of oncomodulin is controlled by a retroviral LTR promoter.

Animals↗

Molecular cloning and nucleotide sequence of a bovine alpha-lactalbumin cDNA.

A cDNA clone for the bovine milk protein, alpha-lactalbumin (alpha LA), has been identified using a rat cDNA probe. The bovine cDNA clone is 703 nucleotides (nt) long, contains 8 nt of 5'-untranslated sequence and 269 nt of 3'-untranslated sequence. When compared with previously reported sequences, the bovine alpha LA mRNA sequence has 74% similarity with rat alpha LA mRNA, 79% similarity with human mRNA and 74% similarity with guinea pig mRNA.

Amino Acid Sequence↗

Keratin K6irs is specific to the inner root sheath of hair follicles in mice and humans.

BACKGROUND: Keratins are a multigene family of intermediate filament proteins that are differentially expressed in specific epithelial tissues. To date, no type II keratins specific for the inner root sheath of the human hair follicle have been identified. OBJECTIVES: To characterize a novel type II keratin in mice and humans. METHODS: Gene sequences were aligned and compared by BLAST analysis. Genomic DNA and mRNA sequences were amplified by polymerase chain reaction (PCR) and confirmed by direct sequencing. Gene expression was analysed by reverse transcription (RT)-PCR in mouse and human tissues. A rabbit polyclonal antiserum was raised against a C-terminal peptide derived from the mouse K6irs protein. Protein expression in murine tissues was examined by immunoblotting and immunofluorescence. RESULTS: Analysis of human expressed sequence tag (EST) data generated by the Human Genome Project revealed a fragment of a novel cytokeratin mRNA with characteristic amino acid substitutions in the 2B domain. No further human ESTs were found in the database; however, the complete human gene was identified in the draft genome sequence and several mouse ESTs were identified, allowing assembly of the murine mRNA. Both species' mRNA sequences and the human gene were confirmed experimentally by PCR and direct sequencing. The human gene spans more than 16 kb of genomic DNA and is located in the type II keratin cluster on chromosome 12q. A comprehensive immunohistochemical survey of expression in the adult mouse by immunofluorescence revealed that this novel keratin is expressed only in the inner root sheath of the hair follicle. Immunoblotting of murine epidermal keratin extracts revealed that this protein is specific to the anagen phase of the hair cycle, as one would expect of an inner root sheath marker. In humans, expression of this keratin was confirmed by RT-PCR using mRNA derived from plucked anagen hairs and epidermal biopsy material. By this means, strong expression was detected in human hair follicles from scalp and eyebrow. Expression was also readily detected in human palmoplantar epidermis; however, no expression was detected in face skin despite the presence of fine hairs histologically. CONCLUSIONS: This new keratin, designated K6irs, is a valuable histological marker for the inner root sheath of hair follicles in mice and humans. In addition, this keratin represents a new candidate gene for inherited structural hair defects such as loose anagen syndrome.

Amino Acid Sequence↗

The P5 multicopy gene family in the MHC is related in sequence to human endogenous retroviruses HERV-L and HERV-16.

P5 is believed to be a multicopy gene family with at least eight members restricted to the major histocompatibility complex (MHC). Although the function of P5 genes is not known, one of the family members, P5-1, was found previously to be specifically transcribed in lymphoid cells and tissue. In this study, we used computer programs Censor and RepeatMasker, and dot plot analysis to show that the major P5 family members are related in sequence to human endogenous retroviruses, HERV-L and HERV-16. The P5-HERV sequences have at least 60% sequence identity with HERV-L within the pol region but differ significantly within the gag and LTR regions. The LTRs flanking the P5-HERV sequences share about 70% identity with the repeat element LTR16B. Structural analysis of open reading frames (ORFs) confirmed that the P5-1 cDNA is characterized by many stop codons and short putative coding regions resembling the patterns found in the HERV-L nucleotide sequence rather than those found in an mRNA sequence such as expressed by HLA class I genes. A 159 base pair (bp) ORF at the 5' end of the 2535 bp P5-1 mRNA may code for a peptide of 52 amino acids with a domain identical in sequence to the signal peptide of HLA molecules. Furthermore, the P5-1 mRNA is complementary in sequence to retroviral pol mRNA. Therefore, the P5-1 genomic sequence appears to be an example of an HERV within the MHC that expresses an antisense transcript with a possible role in immunity to retrovirus infection.

Amino Acid Sequence↗

Two similar but nonallelic rat pancreatic trypsinogens. Nucleotide sequences of the cloned cDNAs.

We have cloned and identified mRNA sequences for two rat pancreatic trypsinogens. Nucleotide sequence analysis of the cloned sequences revealed two mRNAs that encode similar, though noallelic, pretrypsinogens. Trypsinogen I mRNA is 804 nucleotides in length, plus an estimated poly(A) tract of 100 nucleotides, and contains a short (13 nucleotide) 5' noncoding region and a 3' noncoding region of 54 nucleotides. It encodes a preproenzyme of 246 amino acids comprising a hydrophobic prepeptide (signal peptide) of 15 amino acids, an activation peptide characteristic of trypsinogens, and an active form of trypsin, 223 amino acids in length, that has 78% amino acid sequence identity with porcine trypsin. Trypsinogen II mRNA has a nucleotide sequence 88% homologous with that of trypsinogen I mRNA and encodes a protein with 89% amino acid sequence identity with trypsinogen I. The enzymes encoded by trypsinogen I and II mRNAs retain the key amino acid residues that determine the characteristic substrate cleavage preference of trypsins and, therefore, represent the rat counterparts of this digestive enzyme. Trypsinogen I mRNA is a major pancreatic mRNA comprising an estimated 2-5% of the total, whereas trypsinogen II mRNA is present at much lower levels.

Alleles↗

Translational repression in bacteriophage f1: characterization of the gene V protein target on the gene II mRNA.

Previous studies have shown that the single-stranded DNA binding protein of bacteriophage f1 (gene V protein) represses the translation of the mRNA of the phage-encoded replication protein (gene II protein). We have characterized phage mutations in the repressor and in its target. Using a gene II-lacZ translational fusion, we have defined a 16-nucleotide-long region in the gene II mRNA sequence that is required in vivo for repression by the gene V protein. We have shown that in vitro the binding affinity of the gene V protein is at least 10-fold higher to an RNA carrying this sequence than to an RNA lacking it. We propose that this sequence constitutes the gene II mRNA operator.

Base Sequence↗