Bacterial DNA Repair
Genome Dynamics and Function
Centro de Biología Molecular “Severo Ochoa” CSIC-UAM (CBMSO)
DESCRIPTION OF THE OFFER
/Bacterial DNA replication machinery has evolved to copy undamaged DNA in a fast and accurate manner. However, the DNA is continuously exposed to genotoxicants as UV light or chemicals that cause bulky lesions that can block replicative DNA polymerases. Such a blockage can lead to the formation of a single-stranded DNA gaps that induce extensive transcriptional changes known as the SOS response. In the early SOS response, the induced proteins promote failthful DNA repair through homologous recombination. However, if DNA damage persists, bacteria turn to mutagenic DNA repair as a desperate effort to complete DNA replication, allowing replication across the lesions during a process called translesion DNA synthesis (TLS). TLS is performed by specialized DNA polymerases, most of which belong to low-fidelity Y-family DNA polymerases. The action of the TLS polymerases lead to an increased mutagenic risk as these DNA polymerases exhibit a low nucleotide insertion fidelity due to a very open active site designed to accommodate bulky DNA lesions and lack the 3′→5′ exonucleolytic proofreading activity present in high-fidelity DNA polymerases.
To gain a better understanding of bacterial Y-family DNA polymerases:
- We will clone and purify two TLS DNA polymerases from the model bacterium Bacillus subtilis
- By means of the set up of in vitro assays, the TLS polymerases will be studied in their ability to insert nucleotides opposite DNA lesions as well as their capacity to perform further extension. We will analyze the functional complementation between these DNA polymerases as well as their potential interaction with the bacterial processivity factor, the b-clamp.
Biomolecules & Cell D.
Miguel de Vega José