Optimal Random Libraries For the Isolation of Catalytic RNA

The relationship between ribozyme size and catalytic activity is of fundamental importance for RNA catalysis and molecular evolution in the RNA world. We have performed a series of competitive in vitro selection experiments to probe the relationship using RNA libraries containing size-heterogeneous random regions. Our experiments have established an inverse correlation between RNA replication efficiency (the combined efficiency of PCR amplification, transcription, and reverse transcription) and RNA size. A number of ribozyme sequences have been isolated from different RNA size groups under competitive selection conditions. Comprehensive kinetic analysis on isolated ribozymes has revealed that large ribozymes do not confer a significant catalytic superiority over smaller ones under most selection conditions, and actually impose two significant problems of replication inefficiency and RNA misfolding into inactive conformations. The fraction of a misfolded ribozyme population is defined as alpha. Large ribozymes tend to possess high alpha values, which may significantly reduce ribozyme performance. Our results suggest that a random region of around 60 nucleotides represents the optimal balance between ribozyme catalytic activity, RNA misfolding (alpha), and replication efficiency, and may therefore constitute the most advantageous RNA libraries for successful isolation of functional RNA sequences. ©2005 Landes Bioscience

What characteristics of primary care and patients are associated with early death in patients with lung cancer in the UK?

Background: The UK has poor lung cancer survival rates and high early mortality, compared to other countries. We aimed to identify factors associated with early death, and features of primary care that might contribute to late diagnosis. Methods: All cases of lung cancer diagnosed between 2000 and 2013 were extracted from The Health Improvement Network database. Patients who died within 90 days of diagnosis were compared with those who survived longer. Standardised chest X-ray (CXR) and lung cancer rates were calculated for each practice. Results: Of 20 142 people with lung cancer, those who died early consulted with primary care more frequently prediagnosis. Individual factors associated with early death were male sex (OR 1.17; 95% CI 1.10 to 1.24), current smoking (OR 1.43; 95% CI 1.28 to 1.61), increasing age (OR 1.80; 95% CI 1.62 to 1.99 for age ≥80 years compared to 65–69 years), social deprivation (OR 1.16; 95% CI 1.04 to 1.30 for Townsend quintile 5 vs 1) and rural versus urban residence (OR 1.22; 95% CI 1.06 to 1.41). CXR rates varied widely, and the odds of early death were highest in the practices which requested more CXRs. Lung cancer incidence at practice level did not affect early deaths. Conclusions: Patients who die early from lung cancer are interacting with primary care prediagnosis, suggesting potentially missed opportunities to identify them earlier. A general increase in CXR requests may not improve survival; rather, a more timely and appropriate targeting of this investigation using risk assessment tools needs further assessment

RNA-Catalyzed Thioester Synthesis

A series of efficient ribozymes with thioester synthetase activities have been isolated from CoA-linked RNA libraries containing four different lengths (30N, 60N, 100N, and 140N) of random nucleotide regions. Competitive evolution of these size-heterogeneous CoA-RNA libraries resulted in an RNA size population in the order of 30N \u3e 60N \u3e\u3e 100N \u3e 140N. From isolated clones in the 30N and 60N size groups two predominant RNA sequences, TES1 (30N) and TES33 (60N), have been shown to catalyze the synthesis of different thioesters using various acyl adenylates as the substrates. Together with our previous findings, the current results demonstrate a CoA thioester synthetic pathway catalyzed by individual metabolic ribozymes, and suggest a likely mechanism for thioester synthesis and utilization in an RNA world

RNA-Catalyzed Thioester Synthesis

A series of efficient ribozymes with thioester synthetase activities have been isolated from CoA-linked RNA libraries containing four different lengths (30N, 60N, 100N, and 140N) of random nucleotide regions. Competitive evolution of these size-heterogeneous CoA-RNA libraries resulted in an RNA size population in the order of 30N \u3e 60N \u3e\u3e 100N \u3e 140N. From isolated clones in the 30N and 60N size groups two predominant RNA sequences, TES1 (30N) and TES33 (60N), have been shown to catalyze the synthesis of different thioesters using various acyl adenylates as the substrates. Together with our previous findings, the current results demonstrate a CoA thioester synthetic pathway catalyzed by individual metabolic ribozymes, and suggest a likely mechanism for thioester synthesis and utilization in an RNA world

Superior 5\u27 Homogeneity of RNA from ATP-Initiated Transcription Under the T7 Φ2.5 Promoter

Transcription from the commonly used GTP- initiating T7 class III promoter phi6.5 frequently produces heterogeneous RNA at both 3\u27 and 5\u27 ends. We demonstrate here that RNA transcripts from the T7 class II promoter phi2.5 have superior 5\u27 homogeneity over those from the phi6.5 promoter, with comparable total RNA yields. The overall homogeneity of RNA transcripts is improved to different degrees depending on RNA sequences, although transcription under phi2.5 does not affect the 3\u27 heterogeneity of RNA. In combination with 3\u27 RNA trimming by DNAzymes or ribozymes, this ATP- initiated transcription system based on the T7 phi2.5 promoter can provide excellent quality of RNA for applications requiring a high degree of RNA size homogeneity

A Simple and Efficient Method to Prepare Thioesters in Aqueous Solutions

A simple method is described for the efficient synthesis of biologic,ally-active thioesters in aqueous solutions. The method utilizes imidazole as a catalyst and easily synthesized acyl or aminoacyl adenylates to synthesize a variety of thioesters, from small molecules to macromolecules. Yields in excess of 90% can be achieved in less than 10 min at room temperature. Specifically, functional derivatization of RNA with biotin via thioester linkage is demonstrated. (c) 2005 Elsevier Ltd. All rights reserved