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Dual Role for Transactivator Protein C in Activation of mom Promoter of Bacteriophage Mu

Chakraborty, Atanu and Nagaraja, Valakunja (2006) Dual Role for Transactivator Protein C in Activation of mom Promoter of Bacteriophage Mu. In: Journal of Biological Chemistry, 281 (13). pp. 8511-8517.

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Transactivator C protein of bacteriophage Mu activates the mom gene of the phage by an unusual mechanism. DNA binding by C to its site results in unwinding of the neighboring sequences, realigning the out-of-phase promoter elements to facilitate RNA polymerase (RNAP) binding. High level stimulation of a C-independent constitutive promoter mutant (where RNAP is already bound) by the transactivator suggested an additional mechanism of transcription activation at a step after RNAP recruitment. In this study, we have investigated the various steps of promoter-polymerase interactions during transcription initiation by using both the promoter mutant and a positive control (pc) mutant of C protein. The transactivator does not influence formation of the open complex or its stability after facilitating the RNAP binding. However, at a subsequent step, the protein exerts an important role, enhancing the promoter clearance by increasing the productive RNAP·promoter complex. The pc mutant of the transactivator C is compromised at this step, supporting the additional downstream role for C in mom transcription activation. We suggest that this unusual multistep activation of $P_m_o_m$ has evolved to ensure irreversibility of the switch during the late lytic cycle of the phage.

Item Type: Journal Article
Publication: Journal of Biological Chemistry
Publisher: American Society for Biochemistry and Molecular Biology
Additional Information: The Copyright belong to American Society for Biochemistry and Molecular Biology.
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 13 Apr 2006
Last Modified: 27 Aug 2008 11:53
URI: http://eprints.iisc.ac.in/id/eprint/6287

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