Bacillus subtilis bacteriophage SPP1 terminase has a dual activity: it is required for the packaging initiation and represses its own synthesis

• Published in: Gene Vol. 184; no. 2; pp. 251 - 256
• Main Authors: Chai, Sunghee, Szepan, Uwe, Alonso, Juan C
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.01.1997
• Subjects: Bacillus Phages - enzymology; Bacillus Phages - genetics; Bacillus Phages - physiology; Bacillus subtilis; Bacillus subtilis - virology; DNA - biosynthesis; DNA packaging; DNA replication mutant; DNA-Directed RNA Polymerases - metabolism; Endodeoxyribonucleases - genetics; Endodeoxyribonucleases - metabolism; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Viral; Genes, Viral; Late gene; Operon; phage Spp1; Protein Biosynthesis; Sigma Factor - metabolism; Terminase; Transcription control; Transcription, Genetic; Viral Regulatory and Accessory Proteins - genetics; Virus Assembly - physiology; aa, amino acid(s); ndPAGE, non-denaturing PAGE; B., Bacillus; PL, late promoter; Cm, chloramphenicol; DNA replication mutant; kb, kilobase(s) or 1000 bp; RP, RNA polymerase; bp, base pair(s); DNA packaging; R, resistance/resistant; Transcription control; G XP, gene X product; wt, wild type; PAGE, polyacrylamide gel electrophoresis; pfu, plaque-forming unit(s); ts, thermosensitive (mutation); SPP1, B. subtilis bacteriophage SPP1; CL, conditional lethal; Ap, ampicillin; Late gene; Terminase; sus, suppressor sensitive (mutation); EcoRI-X, EcoRI fragment number X; E., Escherichia
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/S0378-1119(96)00609-9

The B. subtilis bacteriophage SPP1 terminase, encoded by genes 1 and 2, is required for the initiation of headful packaging. The DNA segment to which gene 1 product (G 1P) binds includes the pacL and pacR sites and the late PL1 and PL2 promoters from which genes 1 to 7 are transcribed. When SPP1wt or SPP1sus115 (gene 6 −) phages were used to infect a B. subtilis sup 0 strain, the gene 1 to 7 mRNA synthesis was reduced at late times of infection. This was not observed, however, when either chloramphenicol was added 7 min after infection with SPP1wt or when SPP1sus114 (gene 1 −) or SPP1sus19 (gene 2 −) were used to infect B. subtilis sup 0 cells. These results suggest that the terminase enzyme functions as a repressor of its own transcription. G 1P and B. subtilis RNA polymerase (RP) bind to the pacL segment, which contains the PL1 and PL2 promoter region. The binding of G 1P to the pacL site does not seem to exclude RP from the promoters, despite of the overlapping of their binding sites. It is likely that the terminase protein does not repress transcription by a mere steric hindrance of RP binding.