Transcript cleavage activity

The data of Figure 10 illustrate that post-synthetic modification, including hydrolysis, is not limited to proteins. In this example, the large pre-mRNA undergoes post-transcriptional cleavage, splicing, modification of the 3 and 5 ends, and finally methylation to give the specific active mRNA. 

Phosphorothioate-modified DNA aptamers have been selected for binding to NF-kB, ° and phosphoramidate ODNs for binding to TAR to inhibit Tat-mediated transcription. Deoxyribozymes that cleave RNA have been modified with 3 -3 inverted linkages, phosphorothioate linkages, 2 0-methyl sugars and LNA in an attempt to enhance stability and cleavage activity. " ... 

Chedin, S., Riva, M., Schultz, P., Sentenac, A., and Carles, C. (1998). The RNA cleavage activity of RNA polymerase III is mediated by an essential TFHS-like subunit and is important for transcription termination. Genes Dev. 12, 3857-3871. 

Rudd, M. D., Izban, M. G., and Luse, D. S. (1994). The active site of RNA polymerase II participates in transcript cleavage within arrested ternary complexes. Proc. Natl. Acad. Sri. USA 91, 8057-8061. 

Nohmi, T., Battista, J. R., Dodson, L. A., and Walker, G. G. (1988). RecA-mediated cleavage activates UmuD for mutagenesis mechanistic relationship between transcriptional derepression and posttranslational activation. Proc. Natl. Acad. Sci. USA 85, 1816-1820. 

Recently, the related phenomenon of RNA interference (RNAi) has attracted much attention [5]. RNAi occurs when a short (generally 21 nucleotides in length) double-stranded RNA (dsRNA) catalyticaUy represses the translation of a fully complementary mRNA sequence. The process appears to proceed via a complex formed between the antisense RNA strand and a protein with RNase activity [6]. Upon binding to the target mRNA sequence, the ribonucleoprotein complex initiates cleavage of the mRNA transcript thus preventing translation of intact protein. After dissociation from the truncated mRNAs, the ribonucleoprotein complex is free to act on other intact mRNAs. Such small interfering RNAs (siRNAs) have... 

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