The human RNA polymerase I structure reveals an HMG-like docking domain specific to metazoans

Transcription of the ribosomal RNA precursor by RNA polymerase (Pol) I is a major determinant of cellular growth, and dysregulation is observed in many cancer types. Here, we present the purification of human Pol I from cells carrying a genomic GFP fusion on the largest subunit allowing the structural and functional analysis of the enzyme across species. In contrast to yeast, human Pol I carries a single-subunit stalk, and in vitro transcription indicates a reduced proofreading activity. Determination of the human Pol I cryo-EM reconstruction in a close-to-native state rationalizes the effects of disease-associated mutations and uncovers an additional domain that is built into the sequence of Pol I subunit RPA1. This “dock II” domain resembles a truncated HMG box incapable of DNA binding which may serve as a downstream transcription factor–binding platform in metazoans. Biochemical analysis, in situ modelling, and ChIP data indicate that Topoisomerase 2a can be recruited to Pol I via the domain and cooperates with the HMG box domain–containing factor UBF. These adaptations of the metazoan Pol I transcription system may allow efficient release of positive DNA supercoils accumulating downstream of the transcription bubble

Fungal laccases as biocatalysts for wide range applications

32 p.-5 fig.Fungal laccases are multicopper oxidases with high catalytic versatility and low catalytic requirements (only O2 of the air is required for activation). Their high redox potential, especially of certain basidiomycete laccases, significantly increases their oxidation capacity compared to bacterial laccases. These characteristics together provide these enzymes with great potential for applications as biocatalysts in a range of synthetic or degrading reactions. We review here some of the main properties and biotechnological applications of fungal laccases, underlining their overexpression limitations for industrial scale application. We focus on the use of laccases as biocatalysts for organic synthesis, with special emphasis on polymer synthesis.Peer reviewe