Mutations in the β-propeller domain of the Drosophila brain tumor (brat) protein induce neoplasm in the larval brain

Abstract

Inactivation of both alleles of the fruit¯y D. melanogaster brain tumor (brat) gene results in the production of a tumor-like neoplasm in the larval brain, and lethality in the larval third instar and pupal stages. We cloned the brat gene from a transposon-tagged allele and identi®ed its gene product. brat encodes for an 1037 amino acid protein with an N-terminal B-box1 zinc ®nger followed by a B-box2 zinc ®nger, a coiled-coil domain, and a C-terminal b-propeller domain with six blades. All these motifs are known to mediate protein ± protein interactions. Sequence analysis of four brat alleles revealed that all of them are mutated at the bpropeller domain. The clustering of mutations in this domain strongly suggests that it has a crucial role in the normal function of Brat, and de®nes a novel protein motif involved in tumor suppression activity. The brat gene is expressed in the embryonic central and peripheral nervous systems including the embryonic brain. In third instar larva brat expression was detected in the larval central nervous system including the brain and the ventral ganglion, in two glands ± the ring gland and the salivary gland, and in parts of the foregut ± the gastric caecae and the proventriculus. A second brat-like gene was found in D. melanogaster, and homologs were identi®ed in the nematode, mouse, rat, and human. Accumulated data suggests that Brat may regulate proliferation and di erentiation by secretion/transportmediated processes.

Regulation of the Drosophila lin‐41 homologue dappled by let‐7 reveals conservation of a regulatory mechanism within the LIN‐41 subclade

“…Poor conservation of the sixth NHL domain seems common to those RBCC/TRIM proteins represented here with the sixth NHL domain of C. elegans LIN-41, and D. melanogaster BRAT and MEI-P26 proteins having been annotated manually ( Fig. 1, asterisks; Slack and Ruvkun, 1998;Arama et al, 2000;Page et al, 2000). The three-dimensional structure of the NHL domain of BRAT has been determined and the sixth domain does form a portion the ␤-propeller structure (Edwards et al, 2003).…”

“…The expression patterns of all four Drosophila RBCC/TRIMs (DPLD, BRAT, MEI-26, and ABBA) have been partially characterized during embryogenesis (Tomancak et al, 2002), and the expression pattern of brat has been extensively documented in developing adult tissues (Arama et al, 2000;Sonoda and Wharton, 2001;Frank et al, 2002). The four RBCC/TRIM paralogs have very different zygotic transcription patterns, the only exception being an overlap between brat and dpld, which are coexpressed in the developing embryonic central nervous system (CNS; Tomancak et al, 2002).…”

“…They have been shown to participate in numerous distinct processes, including roles in development, both normal and tumorous, asymmetric cell divisions and viral response (Arama et al, 2000;Horn et al, 2004;Bello et al, 2006;Betschinger et al, 2006;Lee et al, 2006;Sakuma et al, 2007) and see Table 2 in Meroni and Diez-Roux (2005), to name but a few. This protein superfamily is characterized by the presence of multiple protein-protein interaction domains, from which it has derived its name, that is, RING, B-box, and coiled-coil domains (Fig.…”

“…BRAT, on the other hand, has been the subject of intense study in recent times (Bello et al, 2006;Betschinger et al, 2006;Lee et al, 2006) and as the name suggests, gives rise to brain tumours when mutated (Woodhouse et al, 1998;Arama et al, 2000). Tumours arising in brat animals are highly proliferative, invasive, transplantable and lethal to the animal (Woodhouse et al, 1998).…”

“…Tumours arising in brat animals are highly proliferative, invasive, transplantable and lethal to the animal (Woodhouse et al, 1998). Of interest, tumorigenic alleles of brat disrupt the NHL repeat region, implicating it as having a direct role in tumor suppression (Arama et al, 2000;Loop et al, 2004). Furthermore, the BRAT NHL domain has been shown to mediate protein-protein interactions of various kinds (Sonoda and Wharton, 2001;Frank et al, 2002), including direct binding to and promoting asymmetric distribution of the cell fate determinant Prospero (Bello et al, 2006;Betschinger et al, 2006;Lee et al, 2006).…”