Steady-state nuclear localization of exportin-t involves RanGTP binding and two distinct nuclear pore complex interaction domains
MOLECULAR AND CELLULAR BIOLOGY
Authors: Kuersten, S; Arts, GJ; Walther, TC; Englmeier, L; Mattaj, IW
Abstract
Vertebrate tRNA export receptor exportin-t (Xpo-t) binds to RanGTP and mature tRNAs cooperatively to form a nuclear export complex. Xpo-t shuttles bidirectionally through nuclear pore complexes (NPCs) but is mainly nuclear at steady state. The steady-state distribution of Xpo-t is shown to depend on its interaction with RanGTP. Two distinct Xpo-t NPC interaction domains that bind differentially to peripherally localized nucleoporins in vitro are identified. The N terminus binds to both Nup153 and RanBP2/Nup358 in a RanGTP-dependent manner, while the C terminus binds to CAN/Nup214 independently of Ran. We propose that these interactions increase the concentration of tRNA export complexes and of empty Xpo-t in the vicinity of NPCs and thus increase the efficiency of the Xpo-t transport cycle.
T cell receptor genotyping and HOXA/TLX1 expression define three T lymphoblastic lymphoma subsets which might affect clinical outcome
CLINICAL CANCER RESEARCH
Authors: Baleydier, Frederic; Decouvelaere, Anne-Valerie; Bergeron, Julie; Gaulard, Philippe; Canioni, Danielle; Bertrand, Yves; Lepretre, Stephane; Petit, Barbara; Dombret, Herve; Beldjord, Kheira; Molina, Thierry; Asnafi, Vahid; Macintyre, Elizabeth
Abstract
Purpose: T lymphoblastic lymphomas (T-LBL) are rare disorders of immature T cells which predominantly involve the mediastinum. Their oncogenic pathways and prognostic variables are not clear. Experimental Design: We undertook a retrospective study of 41 cytoplasmic CD3+ T-LBL (nine cases aged < 16 years) by assessing stage of maturation arrest based on T cell receptor (TCR) immunogenotyping, immunohistochemistry, and quantification of the oncogenes thought to be important in immature T cell malignancies. Results: Application of a TCR-based immunogenetic classification allowed the identification of three subcategories: 11 immature IM0/D-LBL showed no TCR or only incomplete TCRD DJ rearrangement and corresponded to cytoplasmic CD3+ precursors of uncertain lineage. Sixteen mature TCRDdel-LBL showed biallelic TCRD deletion and both TCRG and TCRB rearrangement, consistent with TCR alpha beta lineage restriction. Fourteen intermediate LBL (Int-LBL) showed complete TCRD VDJ and TCRG VJ rearrangement, with TCRB VDJ rearrangement in the majority. All Int-LBL expressed HOX11/TLX1 or HOXA9 transcripts and a proportion of the latter were associated with CALM-AF10 or NUP214-ABL fusion transcripts. IM0/D-LBL were restricted to adults with extrathymic disease and bone marrow involvement, whereas Int-LBL and TCRDdel-LBL were found in children and adults with predominantly thymic disease. In adults, the Int-LBL subgroup was associated with a significantly superior clinical outcome. This subgroup can be identified either by TCR immunogenotyping or HOXA9/TLX1 transcript quantification. Conclusion: Application of this molecular classification will allow the prospective evaluation of prognostic effects within pediatric and adult protocols.