Cloning and characterization of the mouse Interleukin Enhancer Binding Factor 3 (Ilf3) homolog in a screen for RNA binding proteins

In a screen for RNA-binding proteins expressed during murine spermatogenesi s, we have identified a cDNA that encodes a protein of 911 amino acids that contains two copies of the double-stranded RNA-binding motif and has 80% i dentity with human Interleukin Enhancer Binding Factor 3 (ILF3). Linkage an d cytogenetic analyses localized the Ilf3 cDNA to a portion of mouse Chr 9, which shows conserved synteny with a region of human Chr 19 where the huma n ILF3 gene had been previously localized, supporting that we had cloned th e murine homolog of ILF3. Northern analysis indicated the Ilf3 gene is ubiq uitously expressed in mouse adult tissues with high levels of expression in the brain, thymus, testis, and ovary. Polyclonal antibodies detected multi ple protein species in a subset of the tissues expressing Ilf3 RNA. Immunor eactive species are present at high levels in the thymus, testis, ovary, an d the spleen to a lesser extent. The high degree of sequence similarity bet ween the mouse ILF3 protein and other dsRNA binding motif-containing protei ns suggests a role in RNA metabolism, while the differential expression ind icates the mouse ILF3 protein predominantly functions in tissues containing developing lymphocyte and germ cells.