A central region in the minor capsid protein of papillomaviruses facilitates viral genome tethering and membrane penetration for mitotic nuclear entry
Fig 5
Chromosomal association of point mutants of HPV16 L2.
(A) Full-length L2 is depicted with N-terminal, middle and C-terminal functional domains. The minimal chromosomal binding region (CBR) is highlighted in orange. Within the CBR (insert) the nuclear retention signal and the SUMO interaction motif are indicated at their relative location with the CBR. Conserved regions within the CBR are depicted in red, whereas regions with lower conservation are white. Single conserved residues are highlighted. The sites of the point mutations in the CBR are color-coded according to their impact on chromosomal association (black = interfering; grey = silent). (B) The alignment of the amino acid (aa) sequences of the NRS and upstream residues of HPV16, 18, 5, BPV1 and MnPV L2 are written in the single-letter code. The aa residue numbers, and mutated residues (bold font) are denoted for HPV16 L2. The conservation between the indicated L2 aa sequences was scored by PRALINE [78], and obtained scores were grouped into five categories: no (white), low (blue), intermediate-low (green), intermediate-high (orange) and high (red) conservation. (C), (D) The aa substitutions IVAL286AAAA, RR297EE, RR302/5AA and RTR313EEE in HPV16 L2-EGFP were analyzed for chromosomal association during mitosis as in Fig 2C and 2D. (C) Images of wild-type and mutant HPV16 L2-EGFP (upper row, green), H2B-mCherry (center row, red), and merges (lower row) are shown for representative cells. (D) The chromosomal association indices are depicted in a dot plot as in Fig 2D. Statistical significances (two-tailed Student’s t-test) relative to wild-type HPV16 L2-EGFP were assessed (**P < 0.01, ***P < 0.001).