677A Poster - 10. Cell biology: Cytoskeleton, organelles and trafficking
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Shania Kalladanthyil; Miranda Adams; Kaveh Kiani; Luis Rodriguez

Affiliation: Kennesaw State University

Keywords:
o. nucleus; j. muscle

Nuclear domains (ND) are the areas inside the cell nucleus with sharp boundaries and specific protein composition. Mechanisms that control the existence of various nuclear domains are not fully understood. The B-body is a prominent ND that was recently discovered in developing Drosophila flight muscles. We used B-body’s resident protein Bruno 1 (Bru) as a model to dissect out the minimal protein sequence that is required to enable trafficking to this ND. Our study was facilitated by the relatively simple domain structure of Bru, which consists of one paired and one single RNA-recognizing motifs (i.e., RRM1/2 and RRM3), separated by two intrinsically disordered regions (IDR1 and IDR2). RNA-binding ability is critical for B-body affinity since ectopic RNAse treatment releases Bru from B-bodies in muscle cryosections. Using transgenic flies expressing GFP-tagged Bru mutants, we determined that B-body affinity depends on the functionality of RRM1/2, but not RRM3. Next, a series of truncation mutants were deployed to probe for the minimal sequence required for B-body accumulation. Neither the N-terminal IDR1 nor RRM1/2 alone nor in combination could accumulate in the B-body. However, RRM1/2 combined with the C-terminal IDR2 retained B-body affinity. Our study reaffirms the importance of domain combinations for the proper ND trafficking while highlighting the surprising selectivity of IDRs in this process. Future studies should determine if the affinity to B-body can be decoupled from the nuclear functions of the Bru protein.