Stop codons in messenger RNA define when a protein sequence has been completely synthesized; such codons bind release factors (RFs), which cause the newly made protein to be released. Structures of RFs alone and in combination with the ribosome have been reported, but the energetics of the reaction in the presence of codons had not been determined. Here, molecular dynamics simulations of 14 termination complexes are used to define how termination is achieved and how the RFs distinguish different sequences. AUT Johan Sund

Here, the early steps of activator-dependent transcription in yeast are examined by using cryo-electron microscopy to study the transcription activator Rap1 in complex with the general transcription factors TFIID and TFIIA and with yeast enhancer–promoter DNA. A model is proposed whereby interactions between Rap1 and TFIIA convey activating signals to TFIID. Moreover, a Rap1-dependent DNA loop is visualized between the enhancer and the promoter.