Regulation of the mobile genetic element ICEBs1 by a conserved repressor and anti-repressor

The mobile genetic element ICEBs1 is an integrative and conjugative element (a conjugative transposon) found in the Bacillus subtilis chromosome. The SOS response and the RapI-Phrl sensory system activate ICEBsl gene expression, excision, and transfer by inactivating the ICEBsl repressor protein ImmR. Although ImmR is similar to many characterized phage repressors, we found that, unlike these repressors, inactivation of ImmR requires an ICEBslencoded anti-repressor ImmA (YdcM). Under ICEBsl-inducing conditions, ImmA cleaves ImmR at a specific site to induce the element. We found that changing the amount or the specific activity of ImmA can cause derepression of ICEBs1 without activation by RecA or RapI. We isolated and characterized mutations in immA (immAh) that cause derepression of ICEBsl gene expression in the absence of inducing signals. However, we also found that ImmA levels did not significantly change during activation by RapI, indicating that RapI-mediated induction is likely due to increased activity of ImmA. Therefore, we propose that RapI and RecA induce ICEBs1 by increasing its specific activity. Along with earlier observations, some ImmAh mutants highlighted the importance of ImmA's C-terminal sequence for regulation of ImmA protein levels. We demonstrated that GFP tagged with C-terminal residues of ImmA was less abundant in vivo than untagged GFP. We screened cells with mutations of ATP-dependent proteases for effects on ICEBsl expression, and found that ClpXP might play a role in regulating ImmA stability and ICEBs1 gene expression.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Biology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Bose, Baundauna

Advisor dc:contributor.advisor

• Alan D. Grossman.

• Biology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/57672

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/57672