Memory effects of UV exposure

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Contents 1 Group III 1.1 Aim 1.2 Approach 1.3 Testing Bisability in UV-switch strain

Group III

Aim

We are interested in understanding the long term effects of DNA damage in bacterial cells more pertinently

1) Is there an early warning system in bacteria to DNA (UV) Damage?

2) If so, do bacteria remember and communicate the damage?

Approach

So what is this UV damage response and why long term monitoring?

The SOS response

The SOS genetic network consists of various genes that perform diverse functions in response to DNA Damage NER (Nucleotide Excision Repair) Translesion DNA replication Homologous recombination Cell division arrest

Lex A is the master repressor which binds sites in the promoter regions of the genes which are part of the SOS response

RecA acts as a sensor of DNA Damage RecA gets activated and mediates LexA auto-cleavage

Salient features of the SOS response

Transient response induced in response to DNA damage. The promoter activity increases rapidly in the first few minutes and decrease within an hour.

Thus, long time monitoring of DNA Damage induced by UV Irradiation requires that this transient signal generated is stabilized.

So, we tried to couple this transient signal to a bi-stable network to enable long time monitoring of DNA Damage.

Testing Bisability in UV-switch strain

The regulatory network involved in uptake and utilization of lactose exhibits bistability over a range environmental conditions [Ozbudak et al., 2004]. This has been demonstrated in an E.coli strain Muk21 that has chromosomal integration of GFP expressed under lac promoter.

We transformed Muk21 with our UV-switch construct to test hysteresis which is a characteristic behavior of a bistable network.

Ozbudak EM et. al., 2004

Here comes the exciting stuff, the synthetic biology part! We have made the following parts

Now moving onto the actual experiments and the results!!!