Introns Early
Mostrando 13-24 de 103 artigos, teses e dissertações.
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13. Rates of intron loss and gain: Implications for early eukaryotic evolution
We study the intron–exon structures of 684 groups of orthologs from seven diverse eukaryotic genomes and provide maximum likelihood estimates for rates and numbers of intron losses and gains in these same genes for a variety of lineages. Rates of intron loss vary from ≈2 × 10–9 to 2 × 10–10 per year. Rates of gain vary from 6 × 10–13 to 4 × 10�
National Academy of Sciences.
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14. U1 small nuclear RNA and spliceosomal introns in Euglena gracilis
In the flagellated protozoon Euglena gracilis, characterized nuclear genes harbor atypical introns that usually are flanked by short repeats, adopt complex secondary structures in pre-mRNA, and do not obey the GT-AG rule of conventional cis-spliced introns. In the nuclear fibrillarin gene of E. gracilis, we have identified three spliceosomal-type introns tha
The National Academy of Sciences.
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15. A new Drosophila spliceosomal intron position is common in plants
The 25-year-old debate about the origin of introns between proponents of “introns early” and “introns late” has yielded significant advances, yet important questions remain to be ascertained. One question concerns the density of introns in the last common ancestor of the three multicellular kingdoms. Approaches to this issue thus far have relied
National Academy of Sciences.
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16. Relationship between “proto-splice sites” and intron phases: Evidence from dicodon analysis
The coding sequence at the boundaries of exons flanking nuclear introns shows some degree of conservation. To the extent that such sequences might be recognized by the splicing machinery, this conservation may be a derived result of evolution for efficient splicing. Alternatively, such conserved sequences might be remnants of proto-splice sites, which might
National Academy of Sciences.
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17. mRNAs from human adenovirus 2 early region 4.
The molecular structure of the mRNAs from early region 4 of human adenovirus 2 has been studied by Northern blot analysis, S1 nuclease analysis, and sequence analysis of cDNA clones. The results make it possible to identify four different splice donor sites and six different splice acceptor sites. The structure of 12 different mRNAs can be deduced from the a
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18. Differential intron loss and endosymbiotic transfer of chloroplast glyceraldehyde-3-phosphate dehydrogenase genes to the nucleus.
Chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is composed of two different subunits, GAPA and GAPB, which are encoded in the nucleus by two related genes of eubacterial origin. In the present work the genes encoding chloroplast GAPA and GAPB from pea have been cloned and sequenced. The gene for GAPB is split by eight introns. Two introns inter
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19. Intron-dependent evolution of the nucleotide-binding domains within alcohol dehydrogenase and related enzymes.
It has been suggested that the intron/exon structure of a gene corresponds to its evolutionary history. Accordingly, early in evolution DNA segments encoding short functional polypeptides may have been rearranged (exon-shuffling) to create full-length genes and RNA splicing may have been developed to remove intervening sequences (introns) in order to preserv
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20. A Role for SRp54 during Intron Bridging of Small Introns with Pyrimidine Tracts Upstream of the Branch Point
One of the earliest steps in pre-mRNA recognition involves binding of the splicing factor U2 snRNP auxiliary factor (U2AF or MUD2 in Saccharomyces cerevisiae) to the 3′ splice site region. U2AF interacts with a number of other proteins, including members of the serine/arginine (SR) family of splicing factors as well as splicing factor 1 (SF1 or branch poin
American Society for Microbiology.
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21. Structure and expression of murine cytomegalovirus immediate-early gene 2.
The immediate-early gene ie2 of murine cytomegalovirus was characterized. The 1.75-kb ie2 transcript is spliced from three exons, of 78, 124, and 1,283 nucleotides, which are separated by introns of 1,245 and 364 nucleotides. An ATG codon located in the third exon leads into an open reading frame of 391 codons. Immediate-early expression of the predicted pol
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22. Phylogenetic position of yeastlike endosymbionts of anobiid beetles.
The Anobiid beetles Stegobium paniceum and Lasioderma serricorne possess the intracellular yeastlike symbionts Symbiotaphrina buchneri and Symbiotaphrina kochii, respectively, in the mycetome between the foregut and midgut. The nucleotide sequences of the small-subunit rRNA-encoding genes of the symbionts were determined for phylogenetic analysis. Five group
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23. Intron conservation across the prokaryote-eukaryote boundary: structure of the nuclear gene for chloroplast glyceraldehyde-3-phosphate dehydrogenase from maize.
The nuclear gene encoding chloroplast glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from maize has been cloned and sequenced. The gene is G + C rich in its coding sequences and, in addition, contains a CpG-rich region surrounding the promoter. Further upstream several enhancer-like repetitions have been identified that may control the light- and phytochro
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24. Exon definition may facilitate splice site selection in RNAs with multiple exons.
Interactions at the 3' end of the intron initiate spliceosome assembly and splice site selection in vertebrate pre-mRNAs. Multiple factors, including U1 small nuclear ribonucleoproteins (snRNPs), are involved in initial recognition at the 3' end of the intron. Experiments were designed to test the possibility that U1 snRNP interaction at the 3' end of the in