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Regulated nucleo‐cytoplasmic shuttling of human aci‐reductone dioxygenase (hADI1) and its potential role in mRNA processing
Author(s) -
Gotoh Isamu,
Uekita Takamasa,
Seiki Motoharu
Publication year - 2007
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/j.1365-2443.2006.01035.x
Subject(s) - biology , rna splicing , nuclear export signal , nuclear localization sequence , cytoplasm , precursor mrna , nuclear transport , microbiology and biotechnology , cell nucleus , nuclear protein , splicing factor , transcription factor , biochemistry , messenger rna , exon , gene , rna
Bacterial aci‐reductone dioxygenase (ARD), a member of the cupin superfamily, has evolutionarily primitive protein folding and functions in the methionine recycling pathway. Recently, a human ARD orthologue (human ADI1, hADI1) has been identified and exhibits functions other than ARD activity. The hADI1 localizes mainly to the cytoplasm, but a substantial fraction is nuclear, suggesting functions in both cellular compartments. In this study, we report that nucleo‐cytoplasmic transport of hADI1 is regulated by a non‐canonical nuclear export signal (NES) located in the N‐terminal region of hADI1. The NES is composed of multiple basic amino‐acid residues instead of the canonical leucine‐rich sequence. Nuclear export of hADI1 was not mediated by CRM1, a major transporter that binds to leucine‐rich NES. Substitution of the basic residues with alanines abolished NES activity. Mutant hADI1 accumulated in the nucleus and formed speckles frequently observed with splicing factors and some transcription factors. Indeed, hADI1 specifically co‐localized with the splicing factor U1‐70K to the nucleus but not with another splicing factor, SC35. U1‐70K over‐expression induced nuclear accumulation of hADI1. Nuclear hADI1 expression significantly altered the splicing pattern of the adenovirus E1A mini‐gene, which generates multiple alternatively spliced transcripts. Thus, hADI1 may have acquired a novel role in nuclear mRNA processing possibly by modulating U1‐70K‐related functions, an activity negatively regulated by a non‐classical NES sequence.