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. 2022 Mar;28(3):320–339. doi: 10.1261/rna.078964.121

FIGURE 5.

FIGURE 5.

Gcn1 and Gcn20 antagonize frameshifting, but their effects are not mediated primarily by the ISR/GAAC pathway. (A) Schematic of RFP and GLN4(1–99)-(CGA)4 + 1-GFP reporter used in these analyses. (B) Deletion of GCN1 alone or in combination with the RPS3-S104Y mutation results in increased expression of the frameshifted reporter relative to appropriate parent strains. Expression of GCN1 suppresses the frameshifting in the gcn1Δ mutant and in the gcn1Δ RPS3-S104Y double mutant but has no effect on frameshifting in the RPS3-S104Y single mutant. (C) Deletion of GCN1 combined with the mbf1-R89K mutation results in increased expression of the frameshifted reporter relative to either single mutation. Expression of MBF1 suppresses frameshifting in both the mbf1-R89K mutant and in the gcn1Δ mbf1-R89K double mutant. (D) Deletion of GCN1 has only minor effects on the expression of the frameshifted reporter in combination with a deletion of MBF1. (E,F) Deletion of either GCN1 or GCN20 in a wild-type (E) or RPS3-S104Y mutant (F) results in increased expression of the frameshifted reporter when cells are grown in rich (solid bars) or minimal media (checkered bars). Deletions of either GCN2 or GCN4, encoding components of the ISR pathway, result in increased frameshifting only when cells are grown in minimal media (checkered bars). Deletions of other genes encoding proteins that modulate the ISR pathway (YIH1) or interact with Gcn1 on the collided ribosome (GIR2, RBG2) have minimal effects on frameshifting in both conditions. (***) P < 0.001.