Differential effects of single-stranded DNA binding proteins (SSBs) on uracil DNA glycosylases (UDGs) from Escherichia coli and mycobacteria

Purnapatre, Kedar and Handa, Priya and Venkatesh, Jeganathan and Varshney, Umesh (1999) Differential effects of single-stranded DNA binding proteins (SSBs) on uracil DNA glycosylases (UDGs) from Escherichia coli and mycobacteria. In: Nucleic Acids Research, 27 (17). pp. 3487-3492.

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Abstract

Deamination of cytosines results in accumulation of uracil residues in DNA, which unless repaired lead to $GC \rightarrow AT$ transition mutations. Uracil DNA glycosylase excises uracil residues from DNA and initiates the base excision repair pathway to safeguard the genomic integrity. In this study, we have investigated the effect of single-stranded DNA binding proteins (SSBs) from Escherichia coli (EcoSSB) and Mycobacterium tuberculosis (MtuSSB) on uracil excision from synthetic substrates by uracil DNA glycosylases (UDGs) from E.coli, Mycobacterium smegmatis and M.tuberculosis (referred to as Eco-, Msm- and MtuUDGs respectively). Presence of SSBs with all the three UDGs resulted in decreased efficiency of uracil excision from a single-stranded `unstructured' oligonucleotide, SS-U9. On the other hand, addition of EcoSSB to EcoUDG, or MtuSSB to MtuUDG reactions resulted in increased efficiency of uracil excision from a hairpin oligonucleotide containing dU at the second position in a tetraloop (Loop-U2). Interestingly, the efficiency of uracil excision by MsmUDG from the same substrate was decreased in the presence of either Eco- or MtuSSBs. Furthermore, MtuSSB also decreased uracil excision from Loop-U2 by EcoUDG. Our studies using surface plasmon resonance technique demonstrated interactions between the homologous combinations of SSBs and UDGs. Heterologous combinations either did not show detectable interaction (EcoSSB with MtuUDG) or showed a relatively weaker interaction (MtuSSB with EcoUDG). Taken together, our studies suggest differential interactions between the two groups (SSBs and UDGs) of the highly conserved proteins. Such studies may provide important clues to design selective inhibitors against this important class of DNA repair enzymes.

Item Type:	Journal Article
Publication:	Nucleic Acids Research
Publisher:	Oxford University Press
Additional Information:	Copyright of this article belongs to Oxford University Press.
Department/Centre:	Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited:	23 Oct 2007
Last Modified:	19 Sep 2010 04:40
URI:	http://eprints.iisc.ac.in/id/eprint/12167

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