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Datta, Hirock Jyoti,Mandal, Prajna,Bhattacharya, Rajat,Das, Niranjan,Sau, Subrata,Mandal, Nitai Chanda Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.2
Two lysis-defective but DNA synthesis non-defective temperature-sensitive (ts) mutants of mycobacteriophage L1, L1G23ts23 and L1G25ts889 were found to be defective also in phage-specific RNA synthesis in the late period of their growth at 42$^{\circ}C$each to the extent of 50% of that at 32$^{\circ}C$The double mutant, L1G23ts23G25ts889 showed the ts defect in phage RNA synthesis that was nearly additive of those shown individually by the two single-mutant parents. Both G23 and G25 were shown to start functioning sometimes between 30 and 45 min after infection but the former gene might be dispensable after 45 min, while the latter was not. Northern analysis also shows that at 42$^{\circ}C$>, L1G23ts23 affects RNA synthesis more strongly than L1G25ts889 from L1 DNA segments that serve as the template for late gene transcription. Among the 21 virion and 12 non-virion late proteins synthesized by L1, L1G23ts23 is defective in the synthesis of at least 9 virion and all of non-virion proteins at 42$^{\circ}C$>. In contrast, L1G25ts889 is completely defective in synthesis of all the 33 late proteins. Possible roles of G23 and G25 in the positive regulation of transcription of different sets of late genes of L1 have been discussed.
Ganguly, Tridib,Chattoraj, Partho,Das, Malabika,Chanda, Palas K.,Mandal, Nitai.C.,Lee, Chia Y.,Sau, Subrata Korean Society for Biochemistry and Molecular Biol 2004 Journal of biochemistry and molecular biology Vol.37 No.6
The wild-type repressor CI of temperate mycobacteriophage L1 and the temperature-sensitive (ts) repressor CIts391 of a mutant L1 phage, L1cIts391, have been separately overexpressed in E. coli. Both these repressors were observed to specifically bind with the same cognate operator DNA. The operator-binding activity of CIts391 was shown to differ significantly than that of the CI at 32 to $42^{\circ}C$. While 40-95% operator-binding activity was shown to be retained at 35 to $42^{\circ}C$ in CI, more than 75% operator-binding activity was lost in CIts391 at 35 to $38^{\circ}C$, although the latter showed only 10% less binding compared to that of the former at $32^{\circ}C$. The CIts391 showed almost no binding at $42^{\circ}C$. An in vivo study showed that the CI repressor inhibited the growth of a clear plaque former mutant of the L1 phage more strongly than that of the CIts391 repressor at both 32 and $42^{\circ}C$. The half-life of the CIts391-operator complex was found to be about 8 times less than that of the CI-operator complex at $32^{\circ}C$. Interestingly, the repressor-operator complexes preformed at $0^{\circ}C$ have shown varying degrees of resistance to dissociation at the temperatures which inhibit the formation of these complexes are inhibited. The CI repressor, but not that of CIts391, regains most of the DNA-binding activity on cooling to $32^{\circ}C$ after preincubation at 42 to $52^{\circ}C$. All these data suggest that the 131st proline residue at the C-terminal half of CI, which changed to leucine in the CIts391, plays a crucial role in binding the L1 repressor to the cognate operator DNA, although the helix-turn-helix DNA-binding motif of the L1 repressor is located at its N-terminal end.
( Tridib Ganguly ),( Partho Chattoraj ),( Malabika Das ),( Palas K. Chanda ),( Nitai. C. Mandal ),( Chia Y. Lee ),( Subrata Sau ) 생화학분자생물학회 2004 BMB Reports Vol.37 No.6
The wild-type repressor CI of temperate mycobacteriophage Ll and the temperature-sensitive (ts) repressor CIts391 of a mutant Ll phage, LlcIts391, have been separately overexpressed in E. coli. Both these repressors were observed to specifically bind with the same cognate operator DNA. The operator-binding activity of CIts391 was shown to differ significantly than that of the CI at 32 to 42C. While 40-95% operator-binding activity was shown to be retained at 35 to 42C in CI, more than 75% operator-binding activity was lost in CIts391 at 35 to 38℃, although the latter showed only 10% less binding compared to that of the former at 32℃. The CIts391 showed almost no binding at 42℃. An in vivo study showed that the CI repressor inhibited the growth of a clear plaque former mutant of the L1 phage more strongly than that of the CIts391 repressor at both 32 and 42℃. The half-life of the CIts391-operator complex was found to be about 8 times less than that of the CI-operator complex at 32C. Interestingly, the repressor-operator complexes preformed at 0C have shown varying degrees of resistance to dissociation at the temperatures which inhibit the formation of these complexes are inhibited. The CI repressor, but not that of CIts391, regains most of the DNA-binding activity on cooling to 32C after preincubation at 42 to 52C. All these data suggest that the 131 proline residue at the C-terminal half of CI, which changed to leucine in the CIts391, plays a crucial role in binding the L1 repressor to the cognate operator DNA, although the helix-turn-helix DNA-binding motif of the LI repressor is located at its N-terminal end.