Fig. S1. Formation of keratin filaments is observed in GFP-K13-transfected SiHa cells. (A) Immunofluorescence images of SiHa cells transfected with GFP-K13 (green) and stained for keratin (red) show incorporation of GFP-K13 into the endogenous keratin network. Scale bars: 5 m. (B) FRAP analysis of GFP-K13 network recorded over a 2 hour period, 12 hours after transfection, in SiHa cells. The first image was acquired 1 second before bleaching (−1 s); the red arrow indicates the bleached area; subsequent images were acquired after bleaching at the time points indicated. The network appeared to be in a continuous state of flux and GFP-K13 was observed to incorporate into the endogenous keratin IF network at the periphery of the bleached area. (C) Higher-magnification images of time-lapse frames clearly show the ongoing process of filament synthesis at the periphery with new filaments emerging (blue arrow) and existing filaments (yellow and red arrows) merging.

Fig. S2. Fluorescence recovery after photo bleaching monitored in YFP-16E1^E4- transfected SiHa cells. The fluorescence-recovery profile of filamentous YFP-16E1^E4- (blue) depicts a rapid recovery, complete within 30 minutes. This profile suggests that 16E1^E4 is capable of binding to keratin that is already polymerised. Control, unbleached regions (pink) were stable over 2 hours, indicating that results are not affected by either protein synthesis or photo bleaching.

Fig. S3. Colocalization of 16E1^E4 and keratin in HPV16-infected tissue. Tissue was immunostained to detect 16E1^E4 (green) and keratin (red), a DAPI nuclear stain was also included (blue). (A) Reorganisation of the keratin network to the cell periphery is observed in 16E1^E4-positive cells as indicated (arrows). Scale bar: 10 m. (B) Higher-magnification of the area enclosed by the white box in A reveals a filamentous 161^E4 pattern which closely aligns with the keratin IF network. Scale bar: 1 m.

Movie 1. FRAP analysis of the keratin IF network in a single SiHa cell transfected with the GFP-K13 construct. See supplementary material Fig. S1.

Movie 2. FRAP analysis of the 16E1^E4-keratin IF network in a single SiHa cell transfected with the YFP-16E1^E4 construct. See supplementary material Fig. S3.