The NXF gene family in Drosophila: Evolutionary History and Cell-Type Specific Gene Expression
Authors: Martin Calvino; Jae Hak Son; Christopher Ellison
Affiliation: The Human Genetics Institute of New Jersey, Rutgers University
Keywords: u. RNA binding proteins; d. evolution of gene expression
In eukaryotes, mRNAs are transported from the nucleus to the cytoplasm by a family of nuclear RNA export factors (NXF). Members of this protein family are characterized by an amino-terminal region (NTR), an RNA-binding domain (RBD), leucine-rich repeats (LRRs), the NFT2-like domain (NTF2), and a Ubiquitin-associated (UBA) domain. In Drosophila melanogaster, the NXF family is composed of four members that have undergone functional diversification. While Nxf1 is involved in nucleocytoplasmic mRNA export, Nxf2 and Nxf3 were co-opted for piRNA-guided transcriptional silencing of transposable elements (TE). The role of Nxf4 remains to be elucidated. While Nxf1 is ubiquitously expressed, Nxf2 and Nxf3 are predominantly expressed in gonads; and Nxf4 displays testis-specific expression only. In this study, we describe the evolutionary diversification of the NXF gene family across more that 100 species of Drosophila and study branch-specific rates of evolution and test for evidence of positive selection among members of this family. We additionally analyzed publicly available single-cell RNA-seq data to identify cell-type specific expression profiles for NXF family members. Our results provide important insight in the evolution of the NXF gene family and its role in transposon suppression.