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Donald Evans Diego Zorio Margaret MacMorris Carlos E. Winter Kristi Lea Thomas Blumenthal 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(18):9751-9756
The genomes of most eukaryotes are composed of genes arranged on the chromosomes without regard to function, with each gene transcribed from a promoter at its 5′ end. However, the genome of the free-living nematode Caenorhabditis elegans contains numerous polycistronic clusters similar to bacterial operons in which the genes are transcribed sequentially from a single promoter at the 5′ end of the cluster. The resulting polycistronic pre-mRNAs are processed into monocistronic mRNAs by conventional 3′ end formation, cleavage, and polyadenylation, accompanied by trans-splicing with a specialized spliced leader (SL), SL2. To determine whether this mode of gene organization and expression, apparently unique among the animals, occurs in other species, we have investigated genes in a distantly related free-living rhabditid nematode in the genus Dolichorhabditis (strain CEW1). We have identified both SL1 and SL2 RNAs in this species. In addition, we have sequenced a Dolichorhabditis genomic region containing a gene cluster with all of the characteristics of the C. elegans operons. We show that the downstream gene is trans-spliced to SL2. We also present evidence that suggests that these two genes are also clustered in the C. elegans and Caenorhabditis briggsae genomes. Thus, it appears that the arrangement of genes in operons pre-dates the divergence of the genus Caenorhabditis from the other genera in the family Rhabditidae, and may be more widespread than is currently appreciated. 相似文献
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A new structure for the murine Xist gene and its relationship to chromosome choice/counting during X-chromosome inactivation
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Young-Kwon Hong Sara D. Ontiveros Caifu Chen William M. Strauss 《Proceedings of the National Academy of Sciences of the United States of America》1999,96(12):6829-6834
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Internal initiation of translation of five dendritically localized neuronal mRNAs 总被引:10,自引:0,他引:10
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Pinkstaff JK Chappell SA Mauro VP Edelman GM Krushel LA 《Proceedings of the National Academy of Sciences of the United States of America》2001,98(5):2770-2775
In neurons, translation of dendritically localized mRNAs is thought to play a role in affecting synaptic efficacy. Inasmuch as components of the translation machinery may be limiting in dendrites, we investigated the mechanisms by which translation of five dendritically localized mRNAs is initiated. The 5' leader sequences of mRNAs encoding the activity-regulated cytoskeletal protein, the alpha subunit of calcium-calmodulin-dependent kinase II, dendrin, the microtubule-associated protein 2, and neurogranin (RC3) were evaluated for their ability to affect translation in the 5' untranslated region of a monocistronic reporter mRNA. In both neural and nonneural cell lines, the activity-regulated cytoskeletal protein, microtubule-associated protein 2, and alpha-CaM Kinase II leader sequences enhanced translation, whereas the dendrin and RC3 5' untranslated regions slightly inhibited translation as compared with controls. When cap-dependent translation of these constructs was suppressed by overexpression of a protein that binds the cap-binding protein eIF4E, it was revealed that translation of these mRNAs had both cap-dependent and cap-independent components. The cap-independent component was further analyzed by inserting the 5' leader sequences into the intercistronic region of dicistronic mRNAs. All five leader sequences mediated internal initiation via internal ribosome entry sites (IRESes). The RC3 IRES was most active and was further characterized after transfection in primary neurons. Although translation mediated by this IRES occurred throughout the cell, it was relatively more efficient in dendrites. These data suggest that IRESes may increase translation efficiency at postsynaptic sites after synaptic activation. 相似文献
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Sean D. Gallaher Rory J. Craig Iniyan Ganesan Samuel O. Purvine Sean R. McCorkle Jane Grimwood Daniela Strenkert Lital Davidi Melissa S. Roth Tim L. Jeffers Mary S. Lipton Krishna K. Niyogi Jeremy Schmutz Steven M. Theg Crysten E. Blaby-Haas Sabeeha S. Merchant 《Proceedings of the National Academy of Sciences of the United States of America》2021,118(7)