Gene loops juxtapose promoters and terminators in yeast

Mechanistic analysis of transcriptional initiation and termination by RNA polymerase II (Polll) indicates that some factors are common to both processes 1 , 2 . Here we show that two long genes of Saccharomyces cerevisiae,FMP27 and SEN1, exist in a looped conformation, effectively bringing together their promoter and terminator regions. We also show that Polll is located at both ends of FMP27 when this gene is transcribed from a GAL1 promoter under induced and noninduced conditions. Under these conditions, the C-terminal domain of the large subunit of Polll is phosphorylated at Ser5. Notably, inactivation of Kin28p causes a loss of both Ser5 phosphorylation and the loop conformation. These data suggest that gene loops are involved in the early stages of transcriptional activation. They also predict a previously unknown structural dimension to gene regulation, in which both ends of the transcription unit are defined before and during the transcription cycle.