Ring Finger And KH Domain Containing Protein 3 (RKHD3)

Like the other human MEX3 proteins, the deduced 569-amino acid MEX3B protein has an N-terminal nuclear export signal (NES), 2 heterogeneous nuclear ribonucleoprotein K (HNRNPK) homology (KH) domains, and a C-terminal RING finger domain. The KH domains are present in C. elegans Mex3, but not the RING domain. MEX3B also has an N-terminal nuclear localization signal. RT-PCR detected variable expression of MEX3B in human tissues and cell lines, with highest levels in fetal brain, testis, thymus, and salivary gland. Immunohistochemical analysis showed MEX3B expression in goblet cells of adult intestinal epithelium.RNA homopolymer-binding assays and immunoprecipitation analysis revealed that MEX3A, MEX3B, and MEX3C bound RNA via their KH domains in vitro and in vivo.