Isolation of two novel alternative splicing variants of allograft inflammatory factor-1.

Allograft inflammatory factor-1 (AIF-1) was initially cloned from rat cardiac allografts undergoing chronic rejection. AIF-1, possessing an EF-hand-like motif, is thought to be a Ca2+ binding protein. In this study, we identified two novel alternatively spliced variants of AIF-1 by reverse-transcription polymerase chain reaction. One variant encodes an AIF-1 protein that lacks 14 amino acids corresponding to one exon. The other variant encodes a truncated AIF-1 protein due to a frameshift introduced by an 85-bp insertion, and its C-terminal region differs from that of AIF-1. Interestingly, these variants have incomplete and no EF-handlike motifs, respectively. The expression level of the latter variant is high in peripheral blood leukocytes, and it is selectively expressed in macrophage-like cell lines.