PHOTOSENSITIZED FORMATION OF RNA‐PROTEIN CROSSLINKS IN AN INSECT EGG (SMITTZA SPEC., CHIRONOMIDAE, DIPTERA)*

Abstract

Abstract—Upon irradiation of Smittia eggs with ultraviolet light (UV), the extractability of RNA with phenol decreased. The strongest decrease was observed after irradiation at 295 nm wavelength. After trypsin treatment, RNA could be recovered to the same degree as from unirradiated eggs. The extractability of RNA from irradiated eggs was not enhanced by formamide. dimethyl sulfoxide. high salt concentration or heat treatment. The results suggest that the UV‐mediated formation of RNA‐protein crosslinks in Smittia eggs involves the action of a photosensitizer.

Synthesis of a posterior indicator protein in normal embryos and double abdomens of Smittia sp. (Chironomidae, Diptera).

“…Similar phenomena are usually ascribed to light-dependent repair of DNA (8). However, we have demonstrated a lightdependent disappearance of UV-induced pyrimidine dimers from RNA of Smittia embryos (9)(10)(11). A new irradiation technique (12) has enabled us to UV irradiate large numbers of embryos so that virtually all of them form double abdomens and to photorevert a sample so that nearly all of these develop normally again.…”

“…We hypothesize that the anterior determinants might be "masked mRNA." This idea is supported by storage of maternal poly(A)-containing RNA in Smittia eggs (14,27), photoreactivation of UV-inactivated mRNA in Smittia embryos (11), and the observation that after UV irradiation during early intravitelline cleavage, photoreversal of the potential double abdomens can be postponed for several hours without detriment to its efficiency (28). At (29).…”

RNA under attack: Cellular handling of RNA damage

“…RNA-protein crosslinks have been described in UVB-irradiated insect eggs, although the RNAs involved were not identified (Jäckle and Kalthoff, 1979), and in maize (Casati and Walbot, 2004). In the maize study, environmentally relevant doses of UVB caused the formation of covalent crosslinks between protein and RNA within the ribosome.…”