A role for LOS1 in NPC–tDNA contact. (A) Nup60 occupancy at tDNAs. ChIP-qPCR of Nup60-TAP was performed with strains MC177 (wt), MC237 (Δlos1), and MC253 (Δmsn5) during M-phase arrest. Nup60-TAP binding was significantly diminished in the los1 mutant (P-values are in Supplemental Table S4). (B) NPC–tDNA contact with increased LOS1 dosage. ChIP-qPCR of Nup60-TAP was performed with strain MC213 (Δmaf1) transformed with either YEpFAT4-LOS1 or YEpFAT4. Strains were grown in SC-ura,met prior to arrest in M or G1. (C) Diminished nonsense suppression in the absence of NPC–tDNA contact. Fivefold serial dilutions of strains W303-1A (wt), MC206 (Δnup2), MC232 (Δlos1), K5824 (smc3-42), and K5832 (mcd1-73) bearing plasmid pUN60 were spotted on selective plates to measure activity of the plasmid-borne nonsense suppressor SUP11°. (EthGly) 1.5 M EthGly. To compensate for slower growth of strains K5824 and K5832 at 30°C, the cultures were concentrated fivefold and 25-fold, respectively, before diluting serially. Changes in growth of strains K5824 and K5832 in medium containing EthGly is not due to osmotic remediation of the cohesin mutations (Supplemental Fig. S5).