title: Alkylation sensitivity screens reveal a conserved cross-species functionome.
abstract: To identify genes that contribute to chemotherapy resistance in glioblastoma, we conducted a synthetic lethal screen in a chemotherapy-resistant glioblastoma-derived cell line with the clinical alkylator temozolomide (TMZ) and an siRNA library tailored toward "druggable" targets. Select DNA repair genes in the screen were validated independently, confirming the DNA glycosylases uracil-DNA glycosylase (UNG) and A/G-specific adenine DNA glycosylase (MYH) as well as methylpurine-DNA glycosylase (MPG) to be involved in the response to high dose TMZ. The involvement of UNG and MYH is likely the result of a TMZ-induced burst of reactive oxygen species. We then compared the human TMZ sensitizing genes identified in our screen with those previously identified from alkylator screens conducted in Escherichia coli and Saccharomyces cerevisiae. The conserved biologic processes across all three species compose an alkylation functionome that includes many novel proteins not previously thought to impact alkylator resistance. This high-throughput screen, validation and cross-species analysis was then followed by a mechanistic analysis of two essential nodes: base excision repair (BER) DNA glycosylases (UNG, human and mag1, S. cerevisiae) and protein modification systems, including UBE3B and ICMT in human cells or pby1, lip22, stp22 and aim22 in S. cerevisiae. The conserved processes of BER and protein modification were dual targeted and yielded additive sensitization to alkylators in S. cerevisiae. In contrast, dual targeting of BER and protein modification genes in human cells did not increase sensitivity, suggesting an epistatic relationship. Importantly, these studies provide potential new targets to overcome alkylating agent resistance.
authors.affiliation: Departments of Pharmacology& Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213-1863, USA.
authors.forename: David
authors.initials: D
authors.lastname: Svilar
authors.forename: Madhu
authors.initials: M
authors.lastname: Dyavaiah
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Brown
authors.forename: Jiang-bo
authors.initials: JB
authors.lastname: Tang
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Li
authors.forename: Peter R
authors.initials: PR
authors.lastname: McDonald
authors.forename: Tong Ying
authors.initials: TY
authors.lastname: Shun
authors.forename: Andrea
authors.initials: A
authors.lastname: Braganza
authors.forename: Xiao-hong
authors.initials: XH
authors.lastname: Wang
authors.forename: Salony
authors.initials: S
authors.lastname: Maniar
authors.forename: Claudette M
authors.initials: CM
authors.lastname: St Croix
authors.forename: John S
authors.initials: JS
authors.lastname: Lazo
authors.forename: Ian F
authors.initials: IF
authors.lastname: Pollack
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Begley
authors.forename: Robert W
authors.initials: RW
authors.lastname: Sobol
mesh_terms: D000478:Alkylation; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D004249:DNA Damage; D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005909:Glioblastoma / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D000077204:Temozolomide; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D051981:Uracil-DNA Glycosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D018906:Antineoplastic Agents, Alkylating; D001426:Bacterial Proteins; D017382:Reactive Oxygen Species; D003606:Dacarbazine; C482647:UBE3B protein, human; D044767:Ubiquitin-Protein Ligases; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; D051981:Uracil-DNA Glycosidase; C437225:adenine glycosylase; D000077204:Temozolomide