TY  - JOUR
A1  - Tessmer, Ingrid
A1  - Melikishvili, Manana
A1  - Fried, Michael G.
T1  - Cooperative cluster formation, DNA bending and base-flipping by O\(^6\)-alkylguanine-DNA alkyltransferase
JF  - Nucleic Acids Research
N2  - O\(^6\)-Alkylguanine-DNA alkyltransferase (AGT) repairs mutagenic O\(^6\)-alkylguanine and O\(^4\)-alkylthymine adducts in DNA, protecting the genome and also contributing to the resistance of tumors to chemotherapeutic alkylating agents. AGT binds DNA cooperatively, and cooperative interactions are likely to be important in lesion search and repair. We examined morphologies of complexes on long, unmodified DNAs, using analytical ultracentrifugation and atomic force microscopy. AGT formed clusters of 11 proteins. Longer clusters, predicted by the McGhee-von Hippel model, were not seen even at high [protein]. Interestingly, torsional stress due to DNA unwinding has the potential to limit cluster size to the observed range. DNA at cluster sites showed bend angles (similar to 0, similar to 30 and similar to 60 degrees) that are consistent with models in which each protein induces a bend of similar to 30 degrees. Distributions of complexes along the DNA are incompatible with sequence specificity but suggest modest preference for DNA ends. These properties tell us about environments in which AGT may function. Small cooperative clusters and the ability to accommodate a range of DNA bends allow function where DNA topology is constrained, such as near DNA-replication complexes. The low sequence specificity allows efficient and unbiased lesion search across the entire genome.
KW  - inactivation
KW  - nucleotide excision-repair
KW  - atomic-force microscopy
KW  - noncooperative binding
KW  - restricition enzymes
KW  - complex stability
KW  - stranded DNAs
KW  - protein
KW  - chemotherapy
KW  - AGT
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-133949
VL  - 40
IS  - 17
ER  - 
TY  - JOUR
A1  - Bangalore, Disha M.
A1  - Heil, Hannah S.
A1  - Mehringer, Christian F.
A1  - Hirsch, Lisa
A1  - Hemmen, Katharina
A1  - Heinze, Katrin G.
A1  - Tessmer, Ingrid
T1  - Automated AFM analysis of DNA bending reveals initial lesion sensing strategies of DNA glycosylases
JF  - Scientific Reports
N2  - Base excision repair is the dominant DNA repair pathway of chemical modifications such as deamination, oxidation, or alkylation of DNA bases, which endanger genome integrity due to their high mutagenic potential. Detection and excision of these base lesions is achieved by DNA glycosylases. To investigate the remarkably high efficiency in target site search and recognition by these enzymes, we applied single molecule atomic force microscopy (AFM) imaging to a range of glycosylases with structurally different target lesions. Using a novel, automated, unbiased, high-throughput analysis approach, we were able to resolve subtly different conformational states of these glycosylases during DNA lesion search. Our results lend support to a model of enhanced lesion search efficiency through initial lesion detection based on altered mechanical properties at lesions. Furthermore, its enhanced sensitivity and easy applicability also to other systems recommend our novel analysis tool for investigations of diverse, fundamental biological interactions.
KW  - atomic-force microscopy
KW  - base pairs
KW  - molecular structure
KW  - crystal structure
KW  - structural basis
KW  - repair
KW  - recognition
KW  - 8-oxoguanine
KW  - thymine
KW  - mismatches
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-231338
VL  - 10
ER  -