TRF4, the novel TBP-related protein of Drosophila melanogaster, is concentrated at the endoplasmic reticulum and copurifies with proteins participating in the processes associated with endoplasmic reticulum.

Understanding the functions of TBP-related factors is essential for studying chromatin assembly and transcription regulation in higher eukaryotes. The novel TBP-related protein-coding gene, trf4, was described in Drosophila melanogaster. trf4 is found only in Drosophila and has likely originated in Drosophila common ancestor. TRF4 protein has a distant homology with TBP and TRF2 in the region of TBP-like domain and is evolutionarily conserved among distinct Drosophila species, which indicates its functional significance. TRF4 is widely expressed in D. melanogaster with high levels of its expression being observed in testes. Interestingly enough, TRF4 has become a cytoplasmic protein having lost nuclear localization signal sequence. TRF4 is concentrated at the endoplasmic reticulum (ER) and copurifies with the proteins participating in the ER-associated processes. We suggest that trf4 gene is an example of homolog neofunctionalization by protein subcellular relocalization pathway, where the subcellular relocalization of gene product of duplicated gene leads to the new functions in ER-associated processes.