Open AccessRegulation of ascidian Rel by its alternative splice variant
Author(s) -
Kawai Narudo,
Shimada Masumi,
Kawahara Hiroyuki,
Satoh Noriyuki,
Yokosawa Hideyoshi
Publication year - 2003
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1033.2003.03838.x
Subject(s) - cytoplasm , transfection , microbiology and biotechnology , nucleus , nuclear localization sequence , biology , rna splicing , cell nucleus , transcription factor , alternative splicing , nuclear export signal , hek 293 cells , transcription (linguistics) , nuclear protein , subcellular localization , gene , genetics , exon , rna , linguistics , philosophy
The Rel/NF‐κB family of transcription factors play key roles in morphogenesis and immune responses. We reported previously that As‐rel1 and As‐rel2 of the ascidian Halocynthia roretzi are involved in notochord formation. The As‐rel1 protein is a typical Rel/NF‐κB family member, whereas the As‐rel2 protein is a novel truncated product of As‐rel1 that lacks a nuclear localization signal and the unique C‐terminal region. Here, we present conclusive evidence that As‐rel1 and As‐rel2 are generated from a single gene by alternative splicing. We analyzed the roles of As‐rel2 using cells transfected with As‐rel1 or As‐rel2 or both. As‐rel1 was localized in the nucleus and As‐rel2 in the cytoplasm when they were transfected individually. In contrast, when they were transfected simultaneously, both were localized in the nucleus because of the association of As‐rel2 with As‐rel1. In this case, the transcriptional activity of As‐rel1 was suppressed by As‐rel2. Ascidian IκB was found to sequester As‐rel1 in the cytoplasm and suppress its transcriptional activity when As‐rel1 and IκB were transfected simultaneously. In contrast, when As‐rel1 and IκB were transfected together with As‐rel2, As‐rel1 was transported into the nucleus and its transcriptional activity was rescued from inhibition by IκB, whereas As‐rel2 remained localized in the cytoplasm, suggesting IκB sequestration in the cytoplasm by As‐rel2. From these findings, we conclude that the alternative splice variant, As‐rel2, regulates the nuclear localization and transcriptional activity of As‐rel1.