Different P gene editing site-proximal variants are selected in lymphocytic cells.

(A) Strategy for MeV passaging. The original inoculum (p1) was passaged 14 times on Granta cells (L1 to L14) or H358 cells (E1 to E14). L7 was also passaged on H358 cells seven times to generate S14. (B) Genetic variants selected by adaptation to lymphocytic cells (L14). Coding regions on the MeV genome are shown by white boxes and non-coding regions are in black (top). Positions of cell-specific variants above 10% frequency not present in p1 are shown using a black arrowhead, and their allelic percentages and amino acid changes below. The four nearby variants in the P gene (colored) is shown as a sum. A schematic of P gene coding regions and locations of the lymphocytic variants are shown in the middle of panel B. C, generated from an internal AUG start site; P, generated from the first AUG unedited transcript; and V, generated from transcripts with an additional G inserted after the AAAAAGGG sequence (underlined). V shares the first 231 amino acids with P (VN), but has a different C-terminal domain (VC). Variants are indicated by colored arrowheads and their positions relative to the G insertion site (circled) are shown above the arrowheads. The -7 variant (orange) was only detected in passage L7, indicated by an asterisk. Amino acid sequences are shown below the nucleotide sequences. (C) Allelic variants selected after 14 passages in epithelial cells. Conventions as in panel B. (D) Analysis of editing site-proximal variants across passage history. The y-axis shows the percentage reads with the indicated alleles. Alleles are colored as in panel B: WT (grey), -10 (yellow), -9 (blue), -7 (orange), +1(G) (dark green), and +1(A) (light green). The passages analyzed are indicated on the horizontal axis, and the passage history is drawn schematically below it.