Some features of nucleo-cytoplasmic RNA transport from isolated nuclei A. V. Peskin, Y. M. Koen & I. B. Zbarsky Laboratory of Biochemistry, N.K. Koltzov .Institute of Developmental Biology, Academy of Sciences of the USSR, 117808 GSP-1, Moscow 117334, Vavilov Street 26, USSR Abstract Messenger RNA is released preferentially from isolated rat liver nuclei in the presence of the ATP- generating system and cytosol. The release is suppressed by spermidine, while cytoplasmic RNase inhibitor was ineffective and PCMB like some other thiol- blocking agents inhibitory. Cytoplasmic SOD added to the system strongly suppressed RNA release. A similar effect could be obtained by anaerobiosis due to addition of SMP. In both cases the inhibition is reversed by cyanide. In contrast to normal liver where the generation of superoxide radicals takes place almost exclusively in microsomes and is coupled with the oxidation of NADPH, in mouse ascites hepatoma 22a the generation of superoxide radicals occurs mainly in the nuclear envelope and is coupled with the oxidation of both NADPH and NADH and inhibited by cyanide. Introduction The release of messenger RNA to the cytoplasm through the nuclear envelope represents an essen- tial stage of expression of genetic information. The nuclear pore complex appears to possess an imme- diate enzymic mechanism responsible for the ter- minal stages of RNA processing and transport (12, 43). RNA effiux from isolated nuclei is shown to be dependent on temperature, energy and cytoplasmic factors (2, 6, 17, 31, 33, 34). RNA transport is probably essential for cell function and its regulation. In tumor cells the dependence on temperature and ATP is damaged (31, 36, 37); the specificity of transport, namely the screening of RNA types released to the cytoplasm typical of normal cells is also altered (36, 37). A damage of RNA efflux under modification of Abbreviations: PCMB - p-Chloromercuri benzoate; SMP - Submitochondrial particles; SOD Superoxide dismutase. Molec. Biol. Rep. 7,25 30 (1981). 0301 4851/81/0071-0025 $1.20. 9Dr W. Junk Publishers, The Hague. Printed in The Netherlands. ATPase activity has been reported too (1, 6). Thus, the study of nucleo-cytoplasmic transport of RNA in relation to enzymatic activities may be promi- nent interest. A number of effectors affect nucle- oside triphosphatase, phosphatase and RNase ac- tivities of the nuclear envelope (5, 6, 28). In connection to the presence of oxidative systems in the nuclear envelope (44) the oxido-reductases, in particular the NADPH- and NADH-dependent electron transport chains reported in the nuclear envelope (44, 45), especially in respect to formation of superoxide radicals found in ascites carcinoma cell nuclei (8), and reduced SOD activity in tumors (29), may be of interest. We report here the action of some normal cell components on nucleo-cytoplasmic RNA transport and the formation of superoxide radicals in rat liver and mouse 22a hepatoma nuclear envelope. The results have partly been published in Russian (21, 23).