We report the calculation of spectra for various extrasolar Earth-like planets, which characterize their temperatures and atmospheres for evidence of habitability and life. Future space missions such as Darwin and Terrestrial Planet Finder (TPF) will ultimately offer the opportunity to obtain spectra of extrasolar planets situated within the habitable zones of stars and search for signs of life. The atmospheric biosignatures such as ozone, carbon dioxide, and methane, which are abundant in the Earth, could be attributable to primitive life in extrasolar terrestrial planets. In order to explore the possibility of diagnosing the existence of life from spectra, we have calculated synthesized global spectra for hypothetical terrestrial planets. We performed calculations of radiative-convective equilibrium and radiative transfer, taking into account the global cloud distribution, viewing angles, seasonal variation in solar insolation and surface temperatures, and consequently, the infrared radiation emitted to space. The Earth is our only example of a planet whose atmospheric composition is the consequence of the supply of gas from the presence of life. We examine characteristics for the anoxic / low-oxygen atmosphere of the Archean / Proterozoic Earth with the evolution of oxygenic photosynthesis using the photochemical models coupled to radiative-convective equilibrium code. We compare the derived atmospheric spectral feature of extrasolar Earth-like planets with different age and discuss the detectability of atmospheric constituents of extrasolar terrestrial planets.
The hepatitis C virus (HCV) non-structural protein 3 (NS3) is a multifunctional enzyme with protease and helicase activities. It is essential for HCV replication and proliferation and is therefore a target for anti-HCV drugs. To obtain efficient RNA aptamers specific for HCV NS3, and to develop inhibitors of HCV replication, we performed in vitro selection for the NS3 protease and helicase domains, respectively. In vitro selection, namely, SELEX (systematic evolution of ligands by exponential enrichment) is a useful strategy for isolating nucleic acid sequences that have a high affinity for a target molecule from a randomized oligonucleotide pool. Isolated RNA aptamers showed effective inhibition against either the protease or helicase activity of NS3 in vitro. In addition, new type of RNA ligands, which displayed dual-inhibitory functions targeting both NS3 protease and helicase activities were constructed. Furthermore, NS3 protease aptamers effectively inhibited NS3 protease activity in living cells.
Here, I would like to propose the term “RNA world technology”. The RNA world is a hypothetical world that is believed to have been in a period of pre-biotic state. If this is true, the RNA should have various functions to lead the system in the creation of life. In the RNA world, RNAs expressed great versatility. However, not all these functions were brought into modern life. It may be impossible to find out such RNA potential from the modern organisms. “RNA world technology” is the technology that revives and utilizes the RNA functions those might have worked only in the RNA world. Therefore, RNA world technology is distinguished from usual biotechnology. In vitro selection or SELEX is an RNA world technology. Here I show our in vitro selection of subtilisin aptamer (inhibitor) as an example for RNA world technology. Versatility and plasticity of RNAs can be seen from this example. Expectation of “super SELEX” and definition of the term “RNA world” are also discussed.
Recent findings of huge numbers of non-coding RNAs and accumulating reports of gene regulation at the RNA level support the concept of “the RNA world” at the beginning of life on Earth. So the study of RNAs and their enzymes in a hyperthermophilic archaeon, Pyrococcus furiosus, which is believed to be a very ancient organism, may open a new door in the life sciences. We have developed an expression cloning method to classify and identify factors involved in the regulation of RNA metabolism in P. furiosus. Here I propose the value of the systematic analysis of regulatory RNAs and their binding proteins.
Puromycin, an analogue of the 3’ end of aminoacyl-tRNA, is transferred non-specifically to growing polypeptide chains, causing premature termination of translation. However, we found that, at very low concentration, puromycin is transferred specifically to the carboxyl (C-) terminus of the full-length protein. The term puromycin technology refers to methods which have been developed based on this property, including the in vitro virus (IVV) display technique, in which an mRNA (genotype) and its protein (phenotype) are linked via puromycin, and the technique of specific in vitro C-terminal protein labeling. Novel and convenient applications based on puromycin technology have been employed not only for evolutionary protein engineering, such as protein-directed selection, but also in various fields of proteomics research, such as fluorescence labeling, affinity purification (pull-down assay), protein-protein interaction analysis, and protein chips. Here, we review the properties of puromycin that make this technology possible, and the already extensive range of applications of this technology.