Richard Roden

TRIM-NHL proteins are a group of RNA-binding proteins that have long been implicated in post-transcriptional control of vital developmental proteins (Tocchini and Ciosk 2015). These proteins consist of a RING-coiled coil-B Box tripartite motif tethered to an NHL domain. One such protein is Brat, found in Drosophila Melanogaster, though despite being a TRIM-NHL protein Brat does not contain a RING domain. Brat has been extensively studied due to its role in repressing important transcripts such as myc and mad, but until recently was believed to function only in complex with the RNA binding protein Pum (Loedige et al., 2014). Loedige et al., however, discovered that Brat is able to bind RNA via its NHL domain, and is able to act as a post-translational repressor independently of Pum. Since then, further work on Brat has focused on its role as an RNA binding protein. A consensus binding sequence has been identified, and it was found that at least 2 binding sites are needed for Brat to have repressive effects (Loedige et al., 2015). The mechanism of Brat’s repression, however, has remained elusive. Here, using both a tethered and untethered system, we demonstrate that no single domain is able to fully replicate Brat’s repression, and that with the exception of the RNA-binding NHL domain no single domain is necessary for Brat’s repressive function. We also show that a poly-A tail is required for repression by Brat, and that Brat may interact with both Poly-A Binding protein and exonucleases/deadenylases to exert its effects.