共查询到20条相似文献,搜索用时 8 毫秒
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The 5′ untranslated region of the chloroplast psbA mRNA, encoding the D1 protein, is processed in Chlamydomonas reinhardtii. Processing occurs just upstream of a consensus Shine-Dalgarno sequence and results in the removal of 54 nucleotides from the 5′ terminus, including a stem-loop element identified previously as an important structure for D1 expression. Examination of this processing event in C. reinhardtii strains containing mutations within the chloroplast or nuclear genomes that block psbA translation reveals a correlation between processing and ribosome association. Mutations within the 5′ untranslated region of the psbA mRNA that disrupt the Shine-Dalgarno sequence, acting as a ribosome binding site, preclude translation and prevent mRNA processing. Similarly, nuclear mutations that specifically affect synthesis of the D1 protein specifically affect processing of the psbA mRNA. In vitro, loss of the stem-loop element does not prohibit the binding of a message-specific protein complex required for translational activation of psbA upon illumination. These results are consistent with a hierarchical maturation pathway for chloroplast messages, mediated by nuclear-encoded factors, that integrates mRNA processing, message stability, ribosome association, and translation. 相似文献
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Apicomplexan parasites contain so-called apicoplasts, which are similar to chloroplasts of red algae. Multiple alignments of the 5′-leader regions of plastid-encoded genes revealed several conserved noncoding regions in parasites as well as in red algae. The regions were assumed to be sites for RNA interactions with regulatory proteins. Conserved sites were found upstream of ycf24, which is required for [Fe-S] cluster development, and several other genes. In particular, a simultaneous regulation was predicted for ycf24, rps4, and rpo B in Toxoplasma gondii. The prediction agreed with the known data that apicoplasts are only required for a short time, but confer pathogenicity on T. gondii. Another site was predicted upstream of rpo B, which encodes the β subunit of RNA polymerase, in red algae Porphyra spp. and parasites Eimeria tenella and Theileria parva. 相似文献
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Summary The Spec1 and Spec2 mRNAs (Strongylocentrotus purpuratus ectoderm mRNAs) represent a small gene family that encodes 10–12 members of the troponin C superfamily of calcium-binding proteins. These mRNAs and proteins accumulate in the aboral (dorsal) ectoderm of sea urchin embryos and larvae. Using genomic and cDNA clones, we have compared the sequences of four Spec mRNAs: Spec1, Spec2a, Spec2c, and Spec2d. The mRNAs all have at least 120 bases of 5 untranslated leader, approximately 450 bases of open reading frame, and 900 bases (Spec1) or 1250 bases (Spec2a, 2c, 2d) of 3 untranslated trailer. Unexpectedly, when long stretches of 5 untranslated regions or 3 untranslated regions are compared to one another, they are found to be less divergent than the protein-coding regions. Comparing Spec2d, the most divergent member of the family, with the other Spec mRNAs shows that while the protein-coding regions are 60–62% matched, the untranslated regions are greater than 80% matched. Comparisons among Spec1, Spec2a, and Spec2c demonstrate similar but less dramatic conservation of untranslated regions. Our data imply that the Spec gene family has evolved differently from most gene families, with mutations accumulating most rapidly in intron regions, less rapidly in protein-conding regions, and least rapidly in 5 and 3 untranslated regions. 相似文献
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Michael J. Renan 《Bioscience reports》1986,6(9):819-825
In this study, the nucleotide sequences of the 3 untranslated regions (UTR) of the mouse and human c-fos genes, and the rat and human -actin genes were examined. It is shown (i) that the 3 UTR of c-fos is highly conserved between mouse and man, (ii) that multiple copies of a 12 bp element occur, in clusters, in the 3 UTR both of c-fos and of -actin. This conserved 12 bp element is analogous to the putative repressor binding site previously identified (Renan,Bioscience Reports,5 (1985), 739–753). These findings provide additional support for the proposal that regulatory signals are located in the 3 UTR's of certain genes. 相似文献
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Barnes D Franklin S Schultz J Henry R Brown E Coragliotti A Mayfield SP 《Molecular genetics and genomics : MGG》2005,274(6):625-636
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The rate of mRNA decay is an important step in the control of gene expression in prokaryotes, eukaryotes and cellular organelles. Factors that determine the rate of mRNA decay in chloroplasts are not well understood. Chloroplast mRNAs typically contain an inverted repeat sequence within the 3 untranslated region that can potentially fold into a stem-loop structure. These stem-loop structures have been suggested to stabilize the mRNA by preventing degradation by exonuclease activity, although such a function in vivo has not been clearly established. Secondary structures within the translation reading frame may also determine the inherent stability of an mRNA. To test the function of the inverted repeat structures in chloroplast mRNA stability mutants were constructed in the psaB gene that eliminated the 3 flanking sequences of psaB or extended the open reading frame into the 3 inverted repeat. The mutant psaB genes were introduced into the chloroplast genome of Chlamydomonas reinhardtii. Mutants lacking the 3 stem-loop exhibited a 75% reduction in the level of psaB mRNA. The accumulation of photosystem I complexes was also decreased by a corresponding amount indicating that the mRNA level is limiting to PsaB protein synthesis. Pulse-chase labeling of the mRNA showed that the decay rate of the psaB mRNA was significantly increased demonstrating that the stem-loop structure is required for psaB mRNA stability. When the translation reading frame was extended into the 3 inverted repeat the mRNA level was reduced to only 2% of wild-type indicating that ribosome interaction with stem-loop structures destabilizes chloroplast mRNAs. The non-photosynthetic phenotype of the mutant with an extended reading frame allowed us to test whether infrequently used stop codons (UAG and UGA) can terminate translation in vivo. Both UAG and UGA are able to effectively terminate PsaB synthesis although UGA is never used in any of the Chlamydomonas chloroplast genes that have been sequenced. 相似文献
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Peter Gunning Timothy Mohun Sun-Yu Ng Phyllis Ponte Larry Kedes 《Journal of molecular evolution》1984,20(3-4):202-214
Summary The complete 3 untranslated region (3UTR) sequence of the human skeletal-actin gene has been compared with the corresponding regions of the rat and chicken skeletal-actin genes. This comparison reveals that the skeletal-actin 3UTR is composed of conserved and nonconserved segments. By using genomic Southern transfer blots and thermal stability (Tm) measurements, we found that the cardiac-actin gene 3UTR also consists of conserved and nonconserved segments. Comparison of human andXenopus laevis cardiac-actin mRNA sequences confirms the presence of a region of high similarity in the 3UTR. We conclude that subsegments of the 3UTRs of both skeletal- and cardiac-actin genes of birds and mammals are under considerable selective pressure. This suggests that these conserved sequences may have functional roles in actin-gene expression or regulation, and that these roles might be different for each actin isoform. 相似文献
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Uptake of HCO3? and CO2 in Cells and Chloroplasts from the Microalgae Chlamydomonas reinhardtii and Dunaliella tertiolecta 下载免费PDF全文
Gabi Amoroso Dieter Sültemeyer Christoph Thyssen Heinrich P. Fock 《Plant physiology》1998,116(1):193-201
Mass-spectrometric disequilibrium analysis was applied to investigate CO2 uptake and HCO3− transport in cells and chloroplasts of the microalgae Dunaliella tertiolecta and Chlamydomonas reinhardtii, which were grown in air enriched with 5% (v/v) CO2 (high-Ci cells) or in ambient air (low-Ci cells). High- and low-Ci cells of both species had the capacity to transport CO2 and HCO3−, with maximum rates being largely unaffected by the growth conditions. In high- and low-Ci cells of D. tertiolecta, HCO3− was the dominant inorganic C species taken up, whereas HCO3− and CO2 were used at similar rates by C. reinhardtii. The apparent affinities of HCO3− transport and CO2 uptake increased 3- to 9-fold in both species upon acclimation to air. Photosynthetically active chloroplasts isolated from both species were able to transport CO2 and HCO3−. For chloroplasts from C. reinhardtii, the concentrations of HCO3− and CO2 required for half-maximal activity declined from 446 to 33 μm and 6.8 to 0.6 μm, respectively, after acclimation of the parent cells to air; the corresponding values for chloroplasts from D. tertiolecta decreased from 203 to 58 μm and 5.8 to 0.5 μm, respectively. These results indicate the presence of inducible high-affinity HCO3− and CO2 transporters at the chloroplast envelope membrane. 相似文献
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Wen Xian Liu Hua Liang Liu Zhi Jian Chai Xiu Ping Xu Yan Ru Song Le Qing Qu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,121(7):1267-1274
5′ untranslated regions (UTRs) are important sequence elements that modulate the expression of genes. Using the β-glucuronidase
(GUS) reporter gene driven by the GluC promoter for the rice-seed storage-protein glutelin, we evaluated the potential of the 5′-UTRs of six seed storage-protein
genes in enhancing the expression levels of the foreign gene in stable transgenic rice lines. All of the 5′-UTRs significantly
enhanced the expression level of the GluC promoter without altering its expression pattern. The 5′-UTRs of Glb-1 and GluA-1 increased the expression of GUS by about 3.36- and 3.11-fold, respectively. The two 5′-UTRs downstream of the Glb-1, OsAct2 and CMV35S promoters also increased GUS expression level in stable transgenic rice lines or in transient expression protoplasts. Therefore,
the enhancements were independent of the promoter sequence. Real-time quantitative RT-PCR analysis showed that the increase
in protein production was not accompanied by alteration in mRNA levels, which suggests that the enhancements were due to increasing
the translational efficiencies of the mRNA. The 5′-UTRs of Glb-1 and GluA-1, when combined with strong promoters, might be ideal candidates for high production of recombinant proteins in rice seeds. 相似文献
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