Mag1 is a nuclear protein and is involved in the DNA damage response. (A) Strain SO369 (sonA1) was transformed with high-copy plasmids containing the pyrG selectable marker and genes for sonA or mag1. An empty vector containing only the selectable marker was used as a negative control. Transformants were spotted onto media selective for the plasmids with or without 0.02% DEO. Plates were incubated at 42° for 3 days. (B) Time-lapse confocal microscopy of Mag1-GFP (strain JLA263). Mag1-GFP is nuclear during interphase. During mitosis a majority of Mag1-GFP disperses from nuclei while a small percentage remains nuclear, potentially associated with chromatin. See File S1. Bar, 5 μm. (C) Strains R153 (WT), CDS364 (sonB1), JLA264 (mag1Δ), and JLA263 (mag1-GFP) were spotted onto MAGUU plates with or without 0.02% DEO and incubated at either 32° or 42° for 3 days or at 20° for 5 days.