The BRUNOL/CELF family of RNA-binding proteins plays important roles in posttranscriptional regulation and has been implicated in several developmental processes. In this study, we describe the cloning and expression patterns of five Brunol genes in Xenopus laevis. Among them, only Brunol2 is maternally expressed and the zygotic expression of the other four Brunol genes starts at different developmental stages. During Xenopus development, Brunol1, 4-5 are exclusively expressed in the nervous system including domains in the brain, spinal cord, optic and otic vesicles. Brunol2 and 3 are expressed in both the somatic mesoderm and the nervous system. Brunol2 is also extensively expressed in the lens. In transfected Hela cells, BRUNOL1, 2 and 3 proteins are localized in both the cytoplasm and the nucleus, while BRUNOL4 and 5 are only present in the cytoplasm, indicating their different functions. KEY WORDS: Brunol, CELF, Xenopus, expression patternThe BRUNOL (Bruno-like) family of RNA-binding proteins has been implicated in several post-transcriptional regulatory processes including pre-mRNA alternative splicing, mRNA stability and translation. The family was named due to their protein sequence similarity to Drosophila melanogaster Bruno (Good et al., 2000). The same family was also named CELF (CUG-BP1 and ETR-3 Like Factors) (Ladd et al., 2001). For the correspondence between these two systems please refer to Barreau et al. (2006) and Brimacombe and Ladd (2007). BRUNOL family proteins contain three RNA recognition motifs (RRMs), two in the Nterminal region and one in the C-terminal region. The RRMs show a high degree of sequence similarity but the sequences of the linker region between the second and third RRMs are less conserved (Barreau et al., 2006).Mammalian BRUNOL family of proteins contains six members. A phylogenetic analysis suggests that the human BRUNOL proteins fall into two distinct subfamilies: one contains BRUNOL2, 3 (CUG-BP1 and ETR-3), and the other BRUNOL1, 4-6 (CELF3-6) . Brunol2 and 3 are broadly expressed in adult human and mice tissues, with strong expression in the heart, skeletal muscle, and brain (Good et al., 2000;Ladd et al., 2001;. In contrast, Brunol1, 4, 5 and 6 are mainly Int. J. Dev. Biol. 54: 209-214 (2010) expressed in the brain (Good et al., 2000;Ladd et al., 2001;Yang et al., 2007) with Brunol6 also in the kidney and testis . In chicken, 5 Brunol genes have been isolated, with Brunol1 (CELF3) missing. Among them, Brunol2 and 3 (CUG-BP1 and ETR-3) are broadly expressed in the early embryos, while Brunol4-6 (CELF4-6) are restricted primarily to the nervous system (Brimacombe and Ladd, 2007). In addition to Bruno, there are two more Brunol genes in Drosophila, Bru-2 and 3, of which the expressions and functions are still unknown (Delaunay et al., 2004). There are two Brunol homologous genes in C. elegans,[4][5][6]. etr-1 is expressed in muscle cells (Milne and Hodgkin, 1999) while unc-75 in the nervous system (Loria et al., 2003). These data suggest that the two subfamili...

No abstract