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The Role of Dictyostelium UbpA in Nutrient Sensing and the Growth‐to‐Development Transition
Author(s) -
Behrens Michael R.,
Burghart Victoria J.,
Lindsey David F.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1069.6
Subject(s) - biology , dictyostelium , gene , microbiology and biotechnology , mutant , cell growth , mutagenesis , transition (genetics) , nutrient sensing , insertional mutagenesis , genetics , signal transduction
UbpA is a ubiquitin processing protease required for the growth‐to‐development transition during development of the social amoeba Dictyostelium . UbpA, a homolog of yeast Ubp14 and human IsoT/USP5, functions in the disassembly of free polyubiquitin chains. ubpA − cells misregulate genes at the growth‐to‐development transition, do not show EDTA‐resistant cell‐cell adhesion, and fail to aggregate. To identify genes that operate in UbpA‐dependent pathways, we carried out REMI mutagenesis of ubpA − cells and screened for second‐site suppressors of the developmental defects. One suppressor mutant, SU35, developed finger‐like structures and showed EDTA‐resistant cell‐cell adhesion. The SU35 suppressor mutation was located in an open reading frame of 419 codons that could encode a 47.0 kDa protein not similar to any other sequence in the database. Northern analysis indicated that the SU35 gene was expressed in growing wild‐type cells and downregulated upon starvation; in ubpA − cells, it is expressed but not downregulated. In other experiments, we have shown that UbpA is required for the growth‐stage expression of lmcB , which is involved in sensing nutrient levels and signaling cells to develop upon starvation. To elucidate LmcB‐dependent pathways, pulldown experiments utilizing His‐tagged LmcB were used to identify proteins that interact with LmcB. These included UduA3 and the cytidine deaminase, CdaA. Direct binding experiments confirmed the interaction between LmcB and CdaA. cdaA is upregulated at the growth‐to‐development transition. These results will lead to a better understanding of the mechanisms cells use to sense starvation and respond by making the transition from growth to development.