Apoptosis-like programmed cell death induces antisense ribosomal RNA (rRNA) fragmentation and rRNA degradation in Leishmania.

Few natural antisense (as) RNAs have been reported as yet in the unicellular protozoan Leishmania. Here, we describe that Leishmania produces natural asRNAs complementary to all ribosomal RNA (rRNA) species. Interestingly, we show that drug-induced apoptosis-like programmed cell death triggers fragmentation of asRNA complementary to the large subunit gamma (LSU-γ) rRNA, one of the six 28S rRNA processed fragments in Leishmania. Heat and oxidative stress also induce fragmentation of asrRNA, but to a lesser extent. Extensive asrRNA cleavage correlates with rRNA breakdown and translation inhibition. Indeed, overexpression of asLSU-γ rRNA accelerates rRNA degradation upon induction of apoptosis. In addition, we provide mechanistic insight into the regulation of apoptosis-induced asrRNA fragmentation by a 67 kDa ATP-dependent RNA helicase of the DEAD-box subfamily. This helicase binds both sense (s)LSU-γ and asLSU-γ rRNAs, and appears to have a key role in protecting rRNA from degradation by preventing asrRNA cleavage and thus cell death. Remarkably, the asrRNA fragmentation process operates not only in trypanosomatid protozoa but also in mammals. Our findings uncover a novel mechanism of regulation involving asrRNA fragmentation and rRNA breakdown, that is triggered by apoptosis and conditions of reduced translation under stress, and seems to be evolutionary conserved.

Use of zeo-karb 226 and dowex a-l in the analysis of high-purity zinc and zinc-base alloys for Tl and In.

Utility of Zeo-Karb 226 and Dowex A-l for the separation of Tl and In at 5-ppm level from high-purity zinc and zinc-base alloys has been investigated. With Zeo-Karb 226 (NH(4)(+)), T1(+) is conveniently separated from these materials and also from many other cations, with l.0M ammonium nitrate as the eluent. It is subsequently determined with Rhodamine B. This separation principle is also applied to the analysis of Pb-Tl alloys. Both Tl and In (along with Fe) are preconcentrated on Zeo-Karb 226(H(+)) from a solution of the sample at pH 3.0. Suitable methods of subsequent determination of Tl and In are described. In the case of Dowex A-1(H(+)), Tl(+), In(3+), Fe(3+) and Cu(2+) are retained from a solution of the sample at pH 2.0. An o-phenanthroline solution at pH 2.0 elutes all but traces of Cu(2+). In(3+) along with Fe(3+) is eluted with l.0M hydrochloric acid. Finally, Tl is eluted with 2.0M hydrochloric acid containing sulphurous acid.