Interferon Induced Transmembrane Protein 3 (IFITM3)

Genomic sequence analysis determined that all 3 IFITMs contain 2 exons, with the interferon-stimulable response elements (ISREs) in the immediately 5-prime flanking sequence of the promoter/enhancer region. Unlike IFITM1, which has an ISRE and 2 CCAAT boxes but lacks a TATA box, IFITM2 and IFITM3 have 2 ISREs and no TATA or CCAAT boxes.

Sequence analysis predicted that the 133-amino acid IFITM3 protein, which is approximately 90% identical to IFITM2, has an N-terminal signal sequence, 3 potential phosphorylation sites, and a C-terminal leucine zipper. Sequence variability is greatest at the C terminus. Immunoblot analysis showed that in response to IFNA, all 3 IFITMs were expressed as 14-kD proteins that could be further resolved by isoelectric focusing.