In the nematode Caenorhabditis elegans, the 22-nucleotide RNA sequence called the spliced leader (SL) is trans-spliced from the 100-nucleotide-long SL RNA to some mRNAs. We have identified a trans-spliced leader (SL2) whose sequence differs from that of the original spliced leader (SLI), although both are 22 nucleotides long. By primer-extension sequencing, SL2 but not SLi was shown to be present at the 5' end of the mRNA encoded by one of the four glyceraldehyde-3-phosphate dehydrogenase genes. The other three glyceraldehyde-3-phosphate dehydrogenase genes encode mRNAs that have the SLi but not the SL2 sequence at their 5' ends.Therefore, the trans-splicing process can discriminate the transfer of SLi from that of SL2 in a gene-specific manner.The 22 nucleotides (nt) at the 5' end of three of the four actin mRNAs in Caenorhabditis elegans are not encoded contiguously with the protein-encoding portion of the gene (1). This 22-nt untranslated sequence, termed the spliced leader (SL), is identical for all three actin mRNAs. The SL sequence is located in a 1-kilobase (kb) sequence that is tandemly repeated 110 times to form a large array on chromosome V (2, 3). This 1-kb repeat also contains the 5S rRNA gene. This same SL is present on many other mRNAs in addition to actin. It is present in the genomes of all nematodes that have been examined (refs. 4 and 5; S. Bektesh, B. Rosenzweig and D.H., unpublished data). The joining of the SL to the mRNA occurs through trans-splicing between two independently transcribed precursor RNAs, the SL RNA and the mRNA precursor (6). The SL is derived from a 100-nt SL RNA; the 5'-most 22 nt comprise the SL (1). The SL RNA resembles a typical small nuclear RNA, existing in vivo as an anti-Sm antibodyimmunoprecipitable SL small nuclear ribonucleoprotein and possessing a trimethylguanosine cap (7-9).Trans-splicing was first described in trypanosomatid protozoans (10-12). In Trypanosoma brucei, a 39-nt SL, derived from a 140-nt SL RNA, is trans-spliced to all mRNAs. The 1.4-kb repeat unit, which contains the 140-nt SL RNA gene, is present in =200 tandem copies. The SL RNA in trypanosomes has an unusual modified 5' terminus with a 7-methylguanosine cap plus four additional modified o2'_ methyl nucleotides (13,14). The SL RNA transfers this cap structure to the trans-spliced mRNAs. Unlike trypanosomes, in which the 39-nt spliced leader sequence varies in different species and genera, the 22-nt SL is completely conserved in related species and genera of nematodes (refs. 4 and 15; S. Bektesh, B. Rosenzweig, and D.H., unpublished data). However, within a given species of trypanosome, only one SL is present and it is found on all mRNAs (15). We report here that C. elegans contains more than one SL. A second C. elegans SL has been found and designated SL2.* MATERIALS AND METHODSPrimer-Extension Sequencing of RNA. Total RNA was isolated as described (16). Primer-extension sequencing on RNA was done as described by Bektesh et al. (4). Oligonucleotide primer (5 ng) specifically labeled w...

No abstract

No abstract

Animal specimens are easily invaded and corroded by molds, which seriously affects the beautful shape and integrity of biological specimens, It’s led to a huge economic loss. And the traditional methods & agentia of molds controlled are always spoisonous and polluted agentia. In this paper, review the detecting methods of animal specimens infected molds, exploring methods and reagents of prevention of molds,which can make the animal specimens be preserved for a long time without mold damage. This way would be green, environmental-friendly, and protect the human health and reduce economic losses.

No abstract