Antitermination is Required for Readthrough Transcription of the Maize RbcL Gene by a Bacteriophage Promoter in Escherichia Coli

Sequences upstream of the 5' end of the rbcL gene in maize chloroplast fragment Bam 9, have a polar effect on the expression of rbcL from an external upstream bacteriophage PL promoter in Escherichia coli. This polarity can be suppressed by the bacteriophage transcription antitermination protein N or Q. The requirement for transcription antitermination is abolished if DNA upstream of rbcL is removed by a deletion. We have also investigated the ability of RNA polymerase initiating transcription at PL in the presence of N to transcribe through the normal rbcL transcription terminator and into sequences beyond. RNA polymerase initiating at PL can traverse rbcL and its 5' and 3'-flanking regions in the presence of N.