Identification of DRG family regulatory proteins (DFRPs): specific regulation of DRG1 and DRG2.
DRG1 and DRG2 comprise a highly conserved subfamily of GTP-binding proteins and are thought to act as critical regulators of cell growth. Their abnormal expressions may trigger cell transformation or cell cycle arrest. Our aim is to clarify their physiological functions and regulatory mechanisms. Here we report identification of novel proteins, DRG family regulatory protein (DFRP) 1 and DFRP2, which regulate expression of DRG proteins through specific binding. In transient transfection experiments, DFRP1 specifically binds DRG1, and DFRP2 preferentially binds DRG2. DFRPs provide stability to the target DRG proteins through physical association, possibly by blocking the poly-ubiquitination that would precede proteolysis of DRG proteins. DFRPs are highly conserved in eucaryotes, and the expression patterns of dfrp1 and drg1 transcripts in Xenopus embryos and tissues are similar, indicating that these genes work cooperatively in various types of eukaryotic cells. Immunofluorescence experiments have revealed that the interaction between DRG1 and DFRP1 may occur in the cytoplasm. We generated dfrp1- knockout cells and found that endogenous expression of DRG1 is regulated by DFRP1, confirming that DFRP1 is a specific up-regulator of DRG1 in vivo. On the basis of these results, we propose that DRG1 and DRG2 are regulated differently despite their structural similarities.
Ishikawa
Kosuke
K
Division of Cellular and Molecular Biology, Department of Cancer Biology, Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minatoku, Tokyo 108-8639, Japan.
Azuma
Sakura
S
Ikawa
Shuntaro
S
Semba
Kentaro
K
Inoue
Jun-ichiro
J
D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D004625:Embryo, Nonmammalian / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding; D014982:Xenopus laevis / Q000196:embryology / Q000378:metabolism; D000099259:N-myc Downstream-Regulated Gene 1 Protein
D018797:Cell Cycle Proteins; D019204:GTP-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D000099259:N-myc Downstream-Regulated Gene 1 Protein; C078418:developmentally regulated GTP-binding protein