Oral Presentation 16th Asian Conference on Transcription 2019

Single-molecule studies on rho-dependent termination mechanisms of E. coli transcription (1110)

Sungchul Hohng 1 , Eunho Song 1 , Heesoo Uhm 1 , Palinda Munasingha 2 , Yeon-Soo Seo 2 , Kuk Sun Ha 2 , Jin Young Kang 3 , Changwon Kang 2
  1. Seoul National University, Seoul, 1 GWANAK-RO, GWANAK-GU, South Korea
  2. Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, South Korea
  3. Department of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon, South Korea

Rho is a hexameric helicase that induces bacterial transcription termination, but there has been a controversy about the mechanism of rho-dependent termination. In a conventional model called ‘RNA-dependent pathway’, rho first binds rut (rho-utilizing) site of RNA transcript, then chases RNA polymerase (RNAP) waiting on a pausing site, and finally disassembles the transcription complex. In a competing model called ‘RNAP-dependent pathway’, rho makes a stable complex with RNAP, and upon binding the rut site, induces termination through an allosteric mechanism. To clearly elucidate the mechanism of rho-dependent termination, we developed single-molecule fluorescence assays that can monitor the processes of rho-dependent termination of E. coli transcription. We found that whereas both RNA- and RNAP-dependent pathways operate for all tested rho-dependent termination sites with varying proportions, the RNAP-dependent pathway becomes more dominant as the pausing time at the termination site increases. This property of RNAP-dependent termination pathway makes it ideal for riboswitch-based regulation of rho-dependent termination as observed in the leader region of mgtA gene.