Transcriptional regulation of bacteriophage SPO1 protein synthesis in vivo and in vitro.

There are six classes of SPO1 transcripts which are, at least partially, regulated independently of each other. Analysis of proteins made in infections by phage mutants defective in DNA synthesis, or in genes which positively control transcription, permitted each protein to be assigned to one transcription class. Most of the late proteins belong to transcription class m2l. There seem to be few, if any, phage proteins in the l class whose mRNA synthesis depends absolutely on phage DNA synthesis, UV irradiation of host cells allowed the detection of many additional early proteins. The early proteins detected in vivo were compared with proteins synthesized in vitro, using bacterial or gp28 phage-modified RNA polymerase in an Escherichia coli cell-free system. Proteins characterized in vivo as belonging to the e transcription class could be made efficiently in vitro only when transcription was performed by bacterial RNA polymerase. em proteins could be elicited through the use of either bacterial or gp28 polymerase, indicating that their genes can be transcribed in either the early or the middle mode.