title: Synthesis and characterization of DNA minor groove binding alkylating agents.
abstract: Derivatives of methyl 3-(1-methyl-5-(1-methyl-5-(propylcarbamoyl)-1H-pyrrol-3-ylcarbamoyl)-1H-pyrrol-3-ylamino)-3-oxopropane-1-sulfonate (1), a peptide-based DNA minor groove binding methylating agent, were synthesized and characterized. In all cases, the N-terminus was appended with an O-methyl sulfonate ester, while the C-terminus group was varied with nonpolar and polar side chains. In addition, the number of pyrrole rings was varied from 2 (dipeptide) to 3 (tripeptide). The ability of the different analogues to efficiently generate N3-methyladenine was demonstrated as was their selectivity for minor groove (N3-methyladenine) versus major groove (N7-methylguanine) methylation. Induced circular dichroism studies were used to measure the DNA equilibrium binding properties of the stable sulfone analogues; the tripeptide binds with affinity that is >10-fold higher than that of the dipeptide. The toxicities of the compounds were evaluated in alkA/tag glycosylase mutant E. coli and in human WT glioma cells and in cells overexpressing and under-expressing N-methylpurine-DNA glycosylase, which excises N3-methyladenine from DNA. The results show that equilibrium binding correlates with the levels of N3-methyladenine produced and cellular toxicity. The toxicity of 1 was inversely related to the expression of MPG in both the bacterial and mammalian cell lines. The enhanced toxicity parallels the reduced activation of PARP and the diminished rate of formation of aldehyde reactive sites observed in the MPG knockdown cells. It is proposed that unrepaired N3-methyladenine is toxic due to its ability to directly block DNA polymerization.
authors.affiliation: Department of Pharmaceutical Sciences, University of Pittsburgh , Pittsburgh, Pennsylvania 15261, United States.
authors.forename: Prema
authors.initials: P
authors.lastname: Iyer
authors.forename: Ajay
authors.initials: A
authors.lastname: Srinivasan
authors.forename: Sreelekha K
authors.initials: SK
authors.lastname: Singh
authors.forename: Gerard P
authors.initials: GP
authors.lastname: Mascara
authors.forename: Sevara
authors.initials: S
authors.lastname: Zayitova
authors.forename: Brian
authors.initials: B
authors.lastname: Sidone
authors.forename: Elise
authors.initials: E
authors.lastname: Fouquerel
authors.forename: David
authors.initials: D
authors.lastname: Svilar
authors.forename: Robert W
authors.initials: RW
authors.lastname: Sobol
authors.forename: Michael S
authors.initials: MS
authors.lastname: Bobola
authors.forename: John R
authors.initials: JR
authors.lastname: Silber
authors.forename: Barry
authors.initials: B
authors.lastname: Gold
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000737:chemistry; D000477:Alkylating Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000633:toxicity; D000818:Animals; D002417:Cattle; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D045647:DNA Glycosylases / Q000737:chemistry / Q000378:metabolism; D019175:DNA Methylation; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D000477:Alkylating Agents; D029968:Escherichia coli Proteins; C580784:N3-methyladenine; D010455:Peptides; D004247:DNA; C427203:calf thymus DNA; D011065:Poly(ADP-ribose) Polymerases; D045647:DNA Glycosylases; C076131:DNA-3-methyladenine glycosidase II; D000225:Adenine