The hRPC62 subunit of human RNA polymerase III displays helicase activity

In Eukaryotes, tRNAs, 5S RNA and U6 RNA are transcribed by RNA polymerase (Pol) III. Human Pol III is composed of 17 subunits. Three specific Pol III subunits form a stable ternary subcomplex (RPC62-RPC39-RPC32α/β) being involved in pre-initiation complex formation. No paralogues for subunits of this subcomplex subunits have been found in Pols I or II, but hRPC62 was shown to be structurally related to the general Pol II transcription factor hTFIIEα. Here we show that these structural homologies extend to functional similarities. hRPC62 as well as hTFIIEα possess intrinsic ATP-dependent 3′-5′ DNA unwinding activity. The ATPase activities of both proteins are stimulated by single-stranded DNA. Moreover, the eWH domain of hTFIIEα can replace the first eWH (eWH1) domain of hRPC62 in ATPase and DNA unwinding assays. Our results identify intrinsic enzymatic activities in hRPC62 and hTFIIEα.

Nucleic acids in the last stages of maturation of two varieties

Using the MAK column chromatography method the process of wheat grain maturation was found to be closely correlated with nucleic acid metabolism. The amount of nucleic acids in the embryos increased until the end of the maturation of the grain. This increase was the result of an intensive synthesis mainly of rRNA fractions and to some extent also of sRNA. The quantitative proportion of various fractions of nucleic acids also changed in the last stages of grain maturation. In the period of wax maturity in wheat embryos a higher content of 4S and 5S RNA was found which partly explains a higher viability of these seeds.

Comparative analysis of Cassandra TRIMs in three Brassicaceae genomes

Terminal-repeat retrotransposon in miniature (TRIM) elements are a miniature form of retrotransposons and play an important role in genome organization. The Cassandra TRIM family has been identified in over 50 plant species, including both monocots and dicots. Cassandra elements carry an independently transcribed 5S RNA sequence in their terminal repeat regions, which is unique compared with other TRIM families. Although the existence of Cassandra elements has been documented in many plants, much work remains to characterize Cassandra family members and elucidate their distribution. In this study, we comparatively analysed the Cassandra family members in the Brassica oleracea, B. rapa and Arabidopsis thaliana genomes. A total of 602, 451 and 173 members, of which 130, 60 and 9 were relatively intact, were identified from the B. oleracea, B. rapa and A. thaliana genomes, respectively. Most of the Cassandra elements (1120/1226) were found in intergenic spaces, but 106 elements were inserted in genic regions such as introns, exons and untranslated regions. Our comparative analysis of the Cassandra family members in A. thaliana, B. rapa and B. oleracea reveals that some Cassandra elements have been commonly retained during the last 20 million years in three species and some elements have been uniquely evolved in Brassica species. This study promotes our understanding of the role and utility of Cassandra elements in the evolution of the Brassicaceae family.