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Helmut Bertrand Peter Bridge Richard A. Collins Gian Garriga Alan M. Lambowitz 《Cell》1982,29(2):517-526
In Neurospora, the gene encoding the mitochondrial large (25S) ribosomal RNA contains an intervening sequence of 2.3 kb. We have identified eight nuclear mutants that are defective in splicing the mitochondrial large ribosomal RNA and that accumulate unspliced precursor RNA. These mutants identify three different nuclear genes required for the same mitochondrial RNA splicing reaction. Some of the mutants have unique phenotypic characteristics (for example, accumulation of an unusual intron RNA) that may provide insight into specific aspects of mitochondrial RNA splicing. Mutations at one locus, cyt4, are subject to partial phenotypic suppression by the electron-transport inhibitor antimycin. This phenomenon suggests that at least one component required for mitochondrial RNA splicing is regulated such that its synthesis or activity is increased in response to impairment of electron transport. 相似文献
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Structural analyses of mammalian ribosomal ribonucleic acid and its precursors. Nucleotide sequence of ribosomal 5.8 S ribonucleic acid. 总被引:24,自引:0,他引:24
The nucleotide sequence of ribosomal 5.8 S RNA (also known as 7 S or 5.5 S rRNA) from Novikoff hepatoma ascites cells has been determined to be (see article). Estimations of the secondary structure based upon maximized base pairing and the fragments of partial ribonuclease digestion indicate that there may be five base-paired regions in the molecule, three forming a folding of the termini and two forming secondary hairpin loops. The sequence of Novikoff hepatoma 5.8 S rRNA is about 75% homologous with that of yeast 5.8 S rRNA (Rubin, G.M. (1973) J. Biol. Chem. 248, 3860-3875) and similar models for secondary structure are proposed. Both models contain a very stable G-C rich hairpin loop (residues 116 to 138), a less stable A-U-rich hairpin loop (residues 64 to 91) and two symmetrical bulges (residues 15 to 25 and 40 to 44). 相似文献
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RNA splicing in Neurospora mitochondria: nuclear mutants defective in both splicing and 3' end synthesis of the large rRNA 总被引:20,自引:0,他引:20
We have identified nuclear mutants of Neurospora that are defective in splicing the mitochondrial large rRNA and that accumulate unspliced pre-rRNA (35S RNA). In cyt-4 mutants, the unspliced pre-rRNA contains short 3' end extensions (110 nucleotides) that are not present in pre-rRNAs from the other mutants. This and other characteristics suggest that the cyt-4 mutants may be primarily defective in 3' end synthesis and the RNA splicing defect occurs secondarily as a result of impaired RNA folding. The cyt-4 mutants also accumulate a "short" intron RNA and small exon RNAs that may reflect aberrant RNA cleavages. The 5' end of the short intron is about 285 nucleotides downstream from the 5' splice site at or near the base of the "central hairpin", a putative intermediate in folding of the pre-rRNA. Furthermore, the aberrant cleavage sites are immediately after a six nucleotide sequence (GAUAAU) homologous to the final splice junction (GAU/AAC). 相似文献
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Comparison of nucleotide sequences of large T1 ribonuclease fragments of 18S ribosomal RNA of rat and chicken. 总被引:3,自引:3,他引:0
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Nucleotide sequences of large T1 ribonuclease fragments of 18S ribosomal RNA of Novikoff rat ascites hepatoma cells and chicken lymphoblastoid cells were determined and compared. Among the 19 large T1 ribonuclease fragments examined of rat 18S ribosomal RNA, 12 fragments were found to be the same in chicken 18S ribosomal RNA. Three fragments of rat 18S ribosomal RNA were not found among large T1 ribonuclease fragments of chicken 18S ribosomal RNA. Four fragments of rat 18S ribosomal RNA were found to be changed in chicken 18S ribosomal RNA. All the changes were point mutations except the change in the largest T1 ribonuclease fragment 1 which is 21 nucleotides long. 2'-0-methylation at the center of the fragment was lost in chicken 18S ribosomal RNA; all the other nucleotides were the same. 相似文献
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Sequence and hairpin structure of an inverted repeat series at termini of the Physarum extrachromosomal rDNA molecule 总被引:6,自引:0,他引:6
The termini of the 61 kb palindromic rDNA molecules of Physarum polycephalum possess a series of multiple inverted repeats in which are located specific single-strand gaps and tightly attached protein. After treating rDNA with S1 nuclease, we have cloned several 5 kb Eco RI terminal restriction fragments. Sequencing of more than 800 nucleotides from the end of one such clone reveals the presence of six to ten tandemly repeated units averaging 140 +/- 4 bp in length and flanked by Hae III sites. Each 140 nucleotide repeat unit can form thermodynamically stable hairpin structures based on complex internal palindromic components. When the specific gap sequence CCCTA is present, it is located near the apex of a hairpin component. These secondary structures are formed in growing plasmodia, as seen in electron micrographs of native rDNA molecules, which also reveal apparent recombination forms involving rDNA ends and noncontiguous DNA segments. Recombination initiated at terminal single-strand hairpin loops can result in genetic exchange of ribosomal gene sequences and can lead to completion of 5' nucleotide sequences at ends of newly replicated rDNA molecules. 相似文献
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Unusual mRNA pseudoknot structure is recognized by a protein translational repressor 总被引:27,自引:0,他引:27
Translation of ribosomal proteins in the alpha operon of E. coli is repressed by one of the encoded proteins, S4; it specifically recognizes an RNA fragment containing the translational initiation site for the first gene in the operon. RNA structure mapping experiments have suggested a pseudoknot structure for the S4 binding site: the loop of a hairpin is base paired to sequences downstream of the hairpin. Here, we systematically test this proposed structure by measuring S4 binding to an extensive set of site-directed mutations that create compensatory base pair changes in potential helices. The pseudoknot folding is confirmed, and two additional, unexpected interactions within the pseudoknot are also detected. The overall structure is an unusual "double pseudoknot" linking a hairpin upstream of the ribosome binding site with sequences 2-10 codons downstream of the initiation codon. Stabilization of this structure by S4 could account for translational repression. 相似文献
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Interaction of nucleolar phosphoprotein C23 with cloned segments of rat ribosomal deoxyribonucleic acid 总被引:14,自引:0,他引:14
Protein C23, a predominant nucleolar phosphoprotein and a putative nucleolus organizer protein, was analyzed for its general DNA binding characteristics and for its selectivity in binding plasmid DNAs containing cloned fragments of the genes that code for ribosomal RNA (rDNA). By use of nitrocellulose filter disk assays, the protein bound saturably to nuclear DNA with a relatively high affinity. Binding was maximal at low ionic strength (0-0.1 M KCl) with progressively decreasing binding at or above 0.2 M. In competition assays protein C23 showed a marked preference for linear single-stranded vs. double-stranded DNA and little or no affinity for ribosomal RNA. The relative affinities of rDNA sequences for protein C23 were determined with cloned fragments spanning 15.8 kilobases (kb) of DNA starting approximately 3.7 kb upstream from the initiation site for 45S preribosomal RNA to near the 3' end of the sequence coding for 28S RNA. Of the five linearized plasmids tested, only one (pKW1) was an effective competitor for 32P-labeled nuclear DNA. As measured by the concentration of competing DNA required to achieve 50% competition, pKW1 was approximately 20-fold more effective than the second best competitor. The DNA insert in pKW1 is a 3.5-kb sequence which is located in the nontranscribed spacer region less than 0.5 kb upstream from the initiation site for 45S preribosomal RNA. These results suggest that protein C23 has a preference for binding DNA sequences in the nontranscribed spacer of rDNA. 相似文献
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Structure analysis at the ends of the intervening DNA sequences in the chloroplast 23S ribosomal genes of C. reinhardii 总被引:28,自引:0,他引:28
All of the chloroplast 23S ribosomal genes of C. reinhardii are interrupted by a 0.87 kb sequence (Rochaix and Malnoë, 1978). We have sequenced the DNA across the two ends of this intervening element. In parallel, we have examined the nucleotide sequences in the corresponding part of the 23S ribosomal RNA. This allowed us to locate precisely the boundaries between the coding (that is, transcribed into mature 23S rRNA) and the noncoding DNA. The results show that the intervening sequence is flanked by two identical sets of 3 bp (5′-CGT) oriented as direct repeats. In addition, a sequence of 5 bp (5′-CGTGA) lies exactly next to one end and is found very close (16 bp) to the other end, in the coding part of the gene. These two sets are also oriented as direct repeats. Finally, sequences near one end of the intervening element are found with a few alterations near the other end, but in an inverted orientation. Possible interpretations of these results are discussed. 相似文献
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Physical map of Aspergillus nidulans mitochondrial genes coding for ribosomal RNA: an intervening sequence in the large rRNA cistron 总被引:7,自引:0,他引:7
C M Lazarus H Lünsdorf U Hahn P P Stepień H Küntzel 《Molecular & general genetics : MGG》1980,177(3):389-397
Summary A detailed map of the 32 kb mitochondrial genome of Aspergillus nidulans has been obtained by locating the cleavage sites for restriction endonucleases Pst I, Bam H I, Hha I, Pvu II, Hpa II and Hae III relative to the previously determined sites for Eco R I, Hind II and Hind III. The genes for the small and large ribosomal subunit RNAs were mapped by gel transfer hybridization of in vitro labelled rRNA to restriction fragments of mitochondrial DNA and its cloned Eco R I fragment E3, and by electron microscopy of RNA/DNA hybrids.The gene for the large rRNA (2.9 kb) is interrupted by a 1.8 kb insert, and the main segment of this gene (2.4 kb) is separated from the small rRNA gene (1.4 kb) by a spacer sequence of 2.8 kb length.This rRNA gene organization is very similar to that of the two-times larger mitochondrial genome of Neurospora crassa, except that in A. nidulans the spacer and intervening sequences are considerably shorter. 相似文献
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Unique sequence arrangement of ribosomal genes in the palindromic rDNA molecule of Physarum polycephalum. 总被引:5,自引:12,他引:5
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G R Campbell V C Littau P W Melera V G Allfrey E M Johnson 《Nucleic acids research》1979,6(4):1433-1447
R-loop and restriction mapping procedures reveal the organization of coding regions at each end of the giant rDNA palindrome of Physarum polycephalum. A 19S coding region of 2.10 +/- 0.21 kb is located at each end of a very long central spacer (35.64 +/- 2.08 kb). An internal spacer of 1.66 +/- 0.12 kb lies distal to the 19S gene. The 5.8S rRNA coding region is located in this spacer. The 26S gene lies distal to the internal spacer. The 26S gene is unusual among those of eukaryotes in that it consists of 3 coding regions (alpha, beta and gamma) interrupted by 2 intervening sequences. The 26S alpha (most central) coding segment of 2.41 +/- 0.33 kb is separated from the 26S beta segment by an intervening sequence of 0.68 +/- 0.13 kb. The 26S beta segment (0.70 +/- 0.11 kb) is separated from the most distal 26S gamma segment (0.59 +/- 0.14 kb) by an intervening sequence of 1.21 +/- 0.14 kb. The 2 intervening sequences are present in at least 88% of ribsomal genes from active plasmodia, indicating that genes containing these sequences are transcribed. The rDNA termini contain a heterogeneous region which varies in length by +/- 300 base pairs. 相似文献
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1. Several nuclear mutants have been isolated which showed thermo- or cryo-sensitive growth on non-fermentable media. Although the original strain carried mitochondrial drug resistance mutations (CR, ER, OR and PR), the resistance to one or several drugs was suppressed in these mutants. Two of them showed a much reduced amount of the mitochondrial small ribosomal subunit (37S) and of the corresponding 16S ribosomal RNA. Two dimensional electrophoretic analysis did not reveal any change in the position of any of the mitochondrial ribosomal proteins. However one of the mitochondrial ribosomal proteins. However one of the mutants showed a striking decrease in the amounts of three ribosomal proteins S3, S4 and S15. 2. Four temperature-sensitive mitochondrial mutations have been localized in the region of the gene coding for the large mitochondrial ribosomal RNA (23S). These mutants all showed a marked anomaly in the mitochondrial large ribosomal subunit (50S) and/or the corresponding 23S ribosomal RNA. 相似文献