PolyA polymerase

The results include not only RNA polymerases, but DNA polymerases and a polyA polymerase. Select each of the latter and click Remove . 

All classes of RNA transcripts must be processed into mature species. The reactions include several types Nucleolytic cleavage, as in the separation of the mature rRNA species from the primary transcript of RNA polymerase I action Chain extension (non-template-directed), as in the synthesis or regeneration of the common CCA sequence at the 3 end of transfer RNAs or of PolyA at the 3 end of mRNAs and Nucleotide modification, for example, the synthesis of methylated nucleotides in tRNA or rRNA. These reactions are a feature of both prokaryotic and eukaryotic gene expression, and the biological consequences are diverse. For example, modified nucleotides can affect the way in which a tRNA recognizes different codons. 

Polyadenylation occurs at the 3 end of the pre-mRNA. First, the pre-mRNA is cleaved when a specific sequence, AAUAAA, is present in the transcript. Cleavage of the pre-mRNA occurs about 20 or so nucleotides downstream (3 ) of the polyA signal sequence. RNA polymerase II continues on the template, sometimes for as long as... 

It is known that protein synthesis is necessary for BR-induced effects in root tissue (25), and BR-treatment increases nucleic acid and protein synthesis in bean stem (26). In the pea stem segment, kinetic studies with selected protein and nucleic acid synthesis inhibitors showed no evidence for competitive inhibition in polypeptide chain elongation, post-transcriptional polyA addition to heterogeneous RNA, DNA-dependent RNA synthesis, or of the DNA-dependent RNA polymerase... 

Prokaryotic and eukaryotic RNA transcriptions show strong parallels though there are several important differences. A major distinction between prokaryotes and eukaryotes is the move from one prokaryotic enzyme that can faithfully transcribe DNA into RNA to three eukaryotic RNA polymerases. The eukaryotic RNA transcripts are precursors (e.g. pre-mRNA, pre-rRNA and pre-tRNA), which undergo processing to form respective mature RNAs. Furthermore, eukaryotic mRNAs are polyadenylated. A database for mammalian mRNA polyadenylation is available at PolyA DB (http // polya.umdnj.edu/polyadb). The eukaryotic transcription is tightly regulated and various proteins/factors known as transcription factors (TF) are involved in the eukaryotic transcription. The classification of transcription factors can be found at TRANFAC (http //transfac.gbf.de/TRANFAC/cl/cl.html). 

Fig. 8.1. Diagram of a typical eukaryote gene that is transcribed by RNA polymerase II. Control regions upstream of the promoter are involved in the regulation of transcription. The primary transcript is processed to remove the introns. The 5 cap and 3 polyA tail are added before the mature mRNA is transported from the nucleus.

Figure 3. One orientation cloning and its application - Steps for directional cDNA cloning in Agt22. The experimental details of the procedure are presented in the text. At indicates the polyA tail of mRNA, C, G, T indicate the oligonucleotide primer-adapter which has a dC, dG, and dT homopolymer tail, respectively. SP6 and T7 indicate promoters for SP6 and T7 polymerase.

Figure 4. Autoradiogram of [-methionine labeled peptides synthesized in rabbit reticulocyte lysate and immuno-precipitated by a rabbit anti-insulin serum. The RNAs used were 1 pg of Brome Mosaic Virus as a control (lane 1), no RNA (lane 2), 0.5 yg of polyA+ RNA isolated from rat pancreas (lane 3), 0.2 yg of mRNA synthesized by T7 polymerase (lane 4), 0.2 yg of polyA+ RNA combined with 1 yg of antisense mRNA synthesized by SP6 polymerase (lane 5), and 0.2 yg of synthetic mRNA combined with 1 yg of antisense mRNA. The RNAs used in lane 5 and 6 were heated at 70°C for 15 min and cooled slowly before the translation reaction.

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