Point mutations in the Rpb9-homologous domain of Rpc11 that impair transcription termination by RNA polymerase III

RNA polymerase III recognizes and pauses at its terminator, an oligo(dT) tract in non-template DNA, terminates 3′ oligo(rU) synthesis within this sequence, and releases the RNA. The pol III subunit Rpc11p (C11) mediates RNA 3′–5′ cleavage in the catalytic center of pol III during pausing. The amino and carboxyl regions of C11 are homologous to domains of the pol II subunit Rpb9p, and the pol II elongation and RNA cleavage factor, TFIIS, respectively. We isolated C11 mutants from Schizosaccharomyces pombe that cause pol III to readthrough terminators in vivo. Mutant RNA confirmed the presence of terminator readthrough transcripts. A predominant mutation site, F32, resides in the C11 Rpb9-like domain. Another mutagenic approach confirmed the F32 mutation and also isolated I34 and Y30 mutants. Modeling Y30, F32 and I34 of C11 in available cryoEM pol III structures predicts a hydrophobic patch that may interface with C53/37. Another termination mutant, Rpc2-T455I, appears to reside internally, near the RNA–DNA hybrid. We show that the Rpb9 and TFIIS homologous mutants of C11 reflect distinct activities, that differentially affect terminator recognition and RNA 3′ cleavage. We propose that these C11 domains integrate action at the upper jaw and center of pol III during termination

Broadband dielectric and Mossbauer studies of BaTiO3-NiFe2O4 composite multiferroics

A broadband dielectric investigation and Mossbauer studies were performed on 0.7BaTiO(3)-0.3NiFe(2)O(4) composite ceramics prepared from chemically obtained barium titanate and nickel ferrite powders. Dielectric spectroscopy revealed a Debye-type relaxation at frequencies between 10 GHz and 1 THz. The relaxation time slows down on cooling according to the Arrhenius law which can be attributed to the transformation of the system from the paraelectric to the ferroelectric phase through an intermediate relaxor state. The temperature dependence of the center shift of the Mossbauer spectrum was analyzed by applying Debye and Einstein models. Its deviation from these models can be attributed to the anharmonicity. It is also possible that the center shift is affected by the Fe atoms incorporated in BaTiO3 lattice or at the interfaces between BaTiO3 and NiFe2O4

Synthesis and functionalization of rod-like iron oxide nanoparticles

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