title: A new role for translation initiation factor 2 in maintaining genome integrity.
abstract: Escherichia coli translation initiation factor 2 (IF2) performs the unexpected function of promoting transition from recombination to replication during bacteriophage Mu transposition in vitro, leading to initiation by replication restart proteins. This function has suggested a role of IF2 in engaging cellular restart mechanisms and regulating the maintenance of genome integrity. To examine the potential effect of IF2 on restart mechanisms, we characterized its influence on cellular recovery following DNA damage by methyl methanesulfonate (MMS) and UV damage. Mutations that prevent expression of full-length IF2-1 or truncated IF2-2 and IF2-3 isoforms affected cellular growth or recovery following DNA damage differently, influencing different restart mechanisms. A deletion mutant (del1) expressing only IF2-2/3 was severely sensitive to growth in the presence of DNA-damaging agent MMS. Proficient as wild type in repairing DNA lesions and promoting replication restart upon removal of MMS, this mutant was nevertheless unable to sustain cell growth in the presence of MMS; however, growth in MMS could be partly restored by disruption of sulA, which encodes a cell division inhibitor induced during replication fork arrest. Moreover, such characteristics of del1 MMS sensitivity were shared by restart mutant priA300, which encodes a helicase-deficient restart protein. Epistasis analysis indicated that del1 in combination with priA300 had no further effects on cellular recovery from MMS and UV treatment; however, the del2/3 mutation, which allows expression of only IF2-1, synergistically increased UV sensitivity in combination with priA300. The results indicate that full-length IF2, in a function distinct from truncated forms, influences the engagement or activity of restart functions dependent on PriA helicase, allowing cellular growth when a DNA-damaging agent is present.
authors.affiliation: Department of Biochemistry and Molecular and Cellular Biology, Georgetown University Medical Center, Washington, DC, United States of America.
authors.forename: K Elizabeth
authors.initials: KE
authors.lastname: Madison
authors.forename: Mona R
authors.initials: MR
authors.lastname: Abdelmeguid
authors.forename: Erica N
authors.initials: EN
authors.lastname: Jones-Foster
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakai
mesh_terms: D010583:Bacteriophage mu / Q000235:genetics*; D004249:DNA Damage / Q000187:drug effects / Q000528:radiation effects; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics; D004261:DNA Replication / Q000187:drug effects / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D042822:Genomic Instability; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D039881:Prokaryotic Initiation Factor-2 / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D014466:Ultraviolet Rays
chemical_list: D029968:Escherichia coli Proteins; D039881:Prokaryotic Initiation Factor-2; C053139:sulA protein, E coli; D008741:Methyl Methanesulfonate; C506743:priA protein, E coli; D004265:DNA Helicases