Transcriptional specificity after mycobacteriophage I3 infection.
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Date
1987-03
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Abstract
Transcriptional regulation following mycobacteriophage I3 infection has been
investigated. For this purpose, RNA polymerase mutants (rifr) of host bacterium,
Mycobacterium smegmatis have been isolated and characterised. Phage growth in rifs and
rifr cells in presence of rifampicin revealed the involvement of host RNA polymerase in
phage genome transcription. This was confirmed by studies on in vivo RNA synthesis as well
as by direct RNA polymerase assay after phage infection. Significant stimulation in RNA
polymerase activity was seen following phage infection. The maximal levels were attained in
about 60 min post infection and maintained throughout the phage development period. The
stimulation of polymerase activity was most pronounced when the phage DNA was used as
the template. RNA polymerases from uninfected and phage-infected Mycobacterium
smegmatis have been purified to homogeniety. The enzyme purification was accomplished
by a rapid procedure utilising affinity chromatography on rifampicin-Sepharose columns.
Subunit structure analysis of the purified RNA polymerase from uninfected and phageinfected
cells showed the presence of α, β, β' and σ subunits similar to the other prokaryotic
RNA polymerases. In addition, a polypeptide of 79,000 daltons was associated with the
enzyme after phage infection. The enzymes differed in their properties with respect to
template specificity. Phage 13 DNA was the preferred template for the modified RNA
polymerase isolated from infected cells which may account for the transcriptional switch
required for phage development.
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Keywords
RNA polymerase, rifampicin-Sepharose, affinity chromatography, rifampicin resistance, modified RNA polymerase, transcriptional control
Citation
Nagaraja V, Gopinathan K P. Transcriptional specificity after mycobacteriophage I3 infection. Journal of Biosciences. 1987 Mar; 11(1-4): 167-179.