Figure 1

Identification of two conserved motifs unique to the IRF3/7 proteins. (a) Schematic diagram of an IRF3/7 protein. The DNA-binding domain (DBD), the IRF-association domain (IAD), the signal response domain (SRD), as well as the linker region (LK) are shown in different colors. Five well conserved tryptophans (W) in DBD, clusters of positively charged amino acids (+) located in IAD, and phosphorylation sites (P) in SRD are also shown. The amino acid positions of the two motifs (A and B) in the human IRF3 (hIRF3) and 7 (hIRF7) proteins are based on Q14653 and Q92985, respectively. (b) Conserved amino acids found in the two motif regions of IRF3/7 proteins. Sequence logos are used to illustrate the amount of sequence conservation for each position. The overall height of the stack of letters indicates the sequence conservation at each position. The height of symbols within each stack indicates the relative frequency of each amino acid. The multiple sequence alignment was generated using 12 IRF3 and 13 IRF7 protein sequences listed in Supplementary Table S1. The position numbers are based on the multiple sequence alignment (see Supplementary Fig. S2 for the sequence logo for the entire alignment). The two motifs (A and B) are indicated with thick black bars under the logo. Following colors are used for different amino acids: green (K, R, H), blue (D and E), red (A, V, L, I, P, W F, M), and black for all others. (c) Conserved amino acid patterns in other IRF families. Sequence logos were generated from the region corresponding to the motif A. For each IRF subfamily, multiple alignment was generated using 13 IRF protein sequences listed in Supplementary Table S1. The amino acid positions corresponding to the motif A found in the IRF3 and 7 are marked with gray bars under the logo. All sequence logos were generated using WebLogo v2.8.2 (https://weblogo.berkeley.edu)⁶³.