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Szafranski K Glöckner G Dingermann T Dannat K Noegel AA Eichinger L Rosenthal A Winckler T 《Molecular & general genetics : MGG》1999,262(4-5):772-780
Retrotransposable elements are genetic entities which move and replicate within host cell genomes. We have previously reported
on the structures and genomic distributions of two non-long terminal repeat (non-LTR) retrotransposons, DRE and Tdd-3, in
the eukaryotic microorganism Dictyostelium discoideum. DRE elements are found inserted upstream, and Tdd-3 elements downstream, of transfer RNA (tRNA) genes with remarkable position
and orientation specificities. The data set currently available from the Dictyostelium Genome Project led to the characterisation of two repetitive DNA elements which are related to the D. discoideum non-LTR retrotransposon Tdd-3 in both their structural properties and genomic distributions. It appears from our data that
in the D. discoideum genome tRNA genes are major targets for the insertion of mobilised non-LTR retrotransposons. This may be interpreted as the
consequence of a process of coevolution, allowing a viable population of retroelements to transpose without being deleterious
to the small microbial host genome which carries only short intergenic DNA sequences. A new nomenclature is introduced to
designate all tRNA gene-targeted non-LTR retrotransposons (TREs) in the D. discoideum genome. TREs inserted 5′ and 3′ of tRNA genes are named TRE5 and TRE3, respectively. According to this nomenclature DRE and
Tdd-3 are renamed TRE5-A and TRE3-A, respectively. The new retroelements described in this study are named TRE3-B (formerly
RED) and TRE3-C.
Received: 27 May 1999 / Accepted: 23 July 1999 相似文献
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At first sight a protein that is enriched in extracts prepared from nuclei by means of biochemical methods can be considered to be a nuclear protein in vivo. Although this assumption will hold true for most of the analyzed proteins, it could also lead to false interpretations. We analyzed the subcellular distribution of endogenous and plasmid-borne proteins derived from the retrotransposon TRE5-A of Dictyostelium discoideum. In biochemical fractionation experiments the proteins encoded by TRE5-A open reading frame 1 (ORF1p) and the putative endonuclease encoded in ORF2 (ENp) were found in the detergent-insoluble material containing the nuclei. However, salt extraction of isolated nuclei did not considerably release the TRE5-A proteins. Instead, the TRE5-A proteins were strongly enriched in a fraction that contained the chromosomal DNA after removal of most cytoskeletal and histone proteins. These observations implied that ORF1p and ENp were both attached to chromatin in vivo, but this conclusion was disproved by the expression of genetic fusions of green fluorescent protein with either ORF1p or ENp. We show conclusive evidence that both fusion proteins were located as large aggregates of native protein in the cytoplasm of D. discoideum cells. 相似文献
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Eukaryotic genomes are colonized by different retroposons, including short interspersed repetitive elements (SINEs). All currently known SINEs are derived from tRNA and 7SL RNA genes and exploit their type 2 internal pol III promoters. We report here a novel class of SINE elements, called SINE3, derived from 5S rRNA. SINE3s are transcribed from the type 1 internal pol III promoter. Approximately 10,000 copies of SINE3 elements are present in the zebrafish genome, they constitute approximately 0.4% of the genomic DNA. Some elements are as little as 1% diverged from each other, indicating that the retrotransposition of SINE3 in zebrafish is an ongoing process. The 3'-tail of SINE3 is significantly similar to that of CR1-like non-LTR retrotransposons, represented by numerous subfamilies in the zebrafish genome. Analogously to CR1-like elements, SINE3 copies are not flanked by target site duplications, and their 3' termini are composed of (ACATT)n and (ATT)n microsatellites, specific for different subfamilies of SINE3. Given the common structural features, it is highly likely that the enzymatic machinery encoded by CR1-like elements powers proliferation of SINE3. 相似文献
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Terminally redundant sequences in cellular intracisternal A-particle genes. 总被引:21,自引:4,他引:17
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The sequences coding for intracisternal A-particle RNA form a family of related but not identical genetic elements which are present in 650 to 1,000 copies within the mouse genome. We showed that different intracisternal A-particle genes had a terminally redundant sequence of about 400 base pairs, one-half of which arose from the 3' end of the intracisternal A-particle RNA. A second portion of the redundant region did not contain 3-related sequences and was probably derived from the 5' end of intracisternal A-particle RNA. Thus, there were endogenous intracisternal A-particle genes in the cellular DNA-3'-5'--3'-5'-cellular DNA configuration identified for type B and C retroviruses. This indicated that the initial integration of intracisternal A-particle genes into the Mus musculus genome occurred by the same mechanism as the integration of other retroviruses. Two types of heterogeneity were identified among the 5' sequences of the two genes. 相似文献