In an E. coli cell-free translation system, we found that a circular RNA containing an infinite open reading frame produced more translation product than its linear counterpart by two orders of magnitude, because a ribosome can work more effectively towards the elongation on circular RNA than it can on linear RNA. We then tested circular RNAs containing an infinite open reading frame could be translated in eukaryotic systems, in the absence of any particular element for internal ribosome entry, a poly-A tail, or a cap structure. We found that the circular RNAs also produced long peptides in eukaryotic translation systems, possibly owing to the rolling circle amplification mechanism.
Electronic structure of Manganese cluster in photosystem II was investigated by Electron Spin Resonance (ESR) spectroscopy. Spin projections on Mn ions in S2 state manganese cluster were determined by Pulsed Electron-Electron Double Resonance (PELDOR). Protons surrounded manganese cluster were detected by Electron Nuclear Double Resonance (ENDOR). Based on obtained spin projections, ENDOR signals were assigned to the water molecules ligated to manganese cluster. PELDOR technique was applied to the determination of the high affinity Mn2+ site in apo-photosystem II, which is the key site of photo-activation process of manganese cluster.
DNA damage tolerance (DTT) is a cell function to avoid replication arrest by DNA damage during DNA replication. DTT includes two pathways, translesion DNA synthesis (TLS) and template-switched DNA synthesis (TS), regulated by various molecular interactions. TLS is transient DNA synthesis using a damaged template by error-prone DNA polymerases specialized for DNA damage (TLS polymerases). TS, in which one newly synthesized strand is utilized as an undamaged template for replication by replicative polymerases, is error-free process. This review article describes recent progress in structural studies of proteins involved in TLS and TS.