[Detection of a new small RNA, induced by heat shock, in wheat seed ribosomes]

Changes in the small cytoplasmic RNA (scRNA) composition have been examined in wheat embryos exposed to heat shock conditions. A novel scRNA of about 135 nucleotides in length termed as 5.3S RNA, has been detected for the first time. With a rise in temperature from 26 degrees C up to 37 degrees C, the amount of 5.3S RNA increases 5 to 6 times. It was found that 5.3S RNA is localized predominantly on ribosomes and also in the fraction of native 40S ribosomal subunits known to contain translation preinitiation complexes. Upon dissociation of 80S monoribosomes under high ionic strength conditions (0.5 M KCl), 5.3S RNA remains to be bound to the 40S subunit, thus indicating their strong and specific interaction. 5.3S RNA is neither a precursor of the 5S rRNA nor a discrete fragment of high molecular weight ribosomal RNA. It was supposed that 5.3S RNA is transcribed by RNA polymerase III and involved in protein synthesis regulation in plant cells under heat shock conditions at the level of translation initiation.