Photorepair of RNA
This article attempts to describe briefly the current status of our knowledge of repair mechanisms that are operative on RNA. The photorepair mechanisms active on RNA have thus far been unequivocally demonstrated only in plants (Gordon et al., 1975). The phenomenon observed is as follows: When a number of UV-irradiated RNA plant viruses and/or free viral RNAs are assayed on local-lesion hosts, an increase in the specific infectivity is observed when the assay plant is illuminated immediately after the application of the infectious material. This increase in specific infectivity is not seen when heat-inactivated or native infectious material is assayed. Preillumination of the assay host has no effect. On all plants examined, the maximum activity is obtained with black-light, which is far removed from wavelengths which are maximally effective in photosynthesis (Hidalgo-Salvatierra and McLaren, 1969; Murphy and Gordon, 1971a). Photoreactivation (PR) of UV-irradiated tobacco mosaic virus (TMV) RNA has also been observed on white leaves of a variegated mutant host, which lack chlorophyll (McLaren et al., 1970). Photoreactivated sectors ranging from 0.2 to 0.7 have been observed. The extent of repair observed depends upon the virus or viral RNA used, the wavelength used for inactivation, the wavelength used for photoreactivation, and the host plant. The in vivo activity appears to be enzymatic. The ability of Xanthi plants to photoreactivate UV-killed TMV RNA is slowly lost on dark storage.
KeywordsTobacco Mosaic Virus Xeroderma Pigmentosum Pyrimidine Dimer Specific Infectivity Pyrimidine Cyclobutane Dimer
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