The TBC (Tre-2/Bub2/Cdc16) domain protein TRE17 regulates plasma membrane-endosomal trafficking through activation of Arf6
MOLECULAR AND CELLULAR BIOLOGY
Authors: Martinu, L; Masuda-Robens, JM; Robertson, SE; Santy, LC; Casanova, JE; Chou, MM
TBC (Tre-2/Bub2/Cdc16) domains are predicted to encode GTPase-activating proteins (GAPs) for Rab family G proteins. While approximately 50 TBC proteins are predicted to exist in humans, little is known about their substrate specificity. Here we show that TRE17 (also called Tre-2 and USP6), a founding member of the TBC family, targets the Arf family GTPase Arf6, which regulates plasma membrane-endosome trafficking. Surprisingly, TRE17 does not function as a GAP for Arf6 but rather promotes its activation in vivo. TRE17 associates directly with Arf6 in its GDP- but not GTP-bound state. Mapping experiments pinpoint the site of interaction to the TBC domain of TRE17. Forced expression of TRE17 promotes the localization of Arf6 to the plasma membrane, leading to Arf6 activation, presumably due to facilitated access to membrane-associated guanine nucleotide exchange factors (GEFs). Furthermore, TRE17 cooperates with Arf6 GEFs to induce GTP loading of Arf6 in vivo. Finally, short interfering RNA-mediated loss of TRE17 leads to attenuated Arf6 activation. These studies identify TRE17 as a novel regulator of the Arf6-regulated plasma membrane recycling system and reveal an unexpected function for TBC domains.
Fusion of the Lumican (LUM) Gene With the Ubiquitin Specific Peptidase 6 (USP6) Gene in an Aneurysmal Bone Cyst Carrying a t(12;17)(q21;p13) Chromosome Translocation
CANCER GENOMICS & PROTEOMICS
Authors: Panagopoulos, Ioannis; Gorunova, Ludmila; Andersen, Kristin; Lobmaier, Ingvild; Lund-Iversen, Marius; Micci, Francesca; Heim, Sverre
Background/Aim: Aneurysmal bone cyst is a benign bone lesion with a strong tendency to recur. The rearrangement of chromosome band 17p13/USP6 gene is now considered a characteristic genetic feature of aneurysmal bone cyst, with t(16;17)(q22;p13)/CDH11-USP6 as the most frequent chromosomal aberration/fusion gene. We report a novel variant translocation leading to a new fusion gene in an aneurysmal bone cyst. Materials and Methods: Genetic analyses were performed on an aneurysmal bone cyst found in the tibia of a child. Results: G-banding chromosome analysis yielded the karyotype 46,XX,t(12;17)(q21;p13)/46,XX. FISH analysis with a USP6 break-apart probe showed rearrangement of USP6. RNA sequencing detected LUM-USP6 and USP6-LUM fusion transcripts which were subsequently verified by RT-PCR/Sanger sequencing. The two genes exchanged 5'- noncoding exons. Thus, promoter swapping between USP6 and LUM had taken place. Conclusion: We report a novel t(12;17)(q21;p13) chromosome translocation which gave rise to a LUM-USP6 fusion in an aneurysmal bone cyst.