Bot. Bull. Acad. Sin. (1995) 36: 95-100

Chen Chloroplast transcription termination

Quantifying termination of transcription by spinach chloroplast RNA polymerase using supercoiled templates containing tandem copies of the thra terminator

Liang-Jwu Chen

Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan, Republic of China

(Received February 6, 1995; Accepted March 22, 1995)

Abstract. A method was developed to quantify the efficiency with which a transcription terminator of the E. coli threonine attenuator, thra, is recognized by spinach chloroplast RNA polymerase. Multiple tandem copies of the thra terminator were cloned downstream from a strong chloroplast promoter. These supercoiled DNAs were transcribed in vitro and the termination efficiency determined by quantifying the relative amount of transcripts that ended at each successive terminator. A simple calculation showed that about 63% of the RNAs made by spinach chloroplast or T7 RNA polymerase were terminated at each thra terminator.

Keywords: Chloroplast RNA polymerase; Transcription terminator.