Characterization of novel nuclear targeting and apoptosis-inducing domains in FAS associated factor 1.
FAS associated factor 1 (FAF1) has been described as an unusual protein that binds to the intracellular portion of the apoptosis signal transducing receptor FAS/Apo-1 and potentiates apoptosis in L-cells. By means of mRNA differential display we have identified the avian homologue (qFAF) as a fibroblast growth factor-inducible gene in pluripotent cells from E0 quail embryos during mesoderm induction in vitro. Later during embryonic development, qFAF expression is ubiquitous. We confirm that qFAF is associated with FAS, and show that it is phosphorylated on serine residues and localized to the nucleus. By in vitro mutagenesis we have delimited a novel nuclear targeting domain to a short 35 amino acid &agr ;-helical region in the amino-terminal half of the protein. The nuclear function of qFAF remains unclear. However, a probably dominant negative deletion mutant of qFAF causes apoptosis of transfected cells. This function resides in the carboxy-terminal domain of qFAF which shares remarkable sequence homologies with a putative ubiquitin conjugating enzyme from Caenorhabditis elegans. Our data indicate a complex function for FAF, which may be executed during FAS signalling and/or in the ubiquitination pathway, and may be essential for cell differentiation and survival.
Fröhlich
T
T
Max-Planck-Institut für physiologische und Klinische Forschung, W. G. Kerckhoff-Institut, Abteilung Molekulare Zellbiologie, Parkstrasse 1, D-61231 Bad Nauheim, Germany.
Risau
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W
Flamme
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I
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000235:genetics* / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology*; D002467:Cell Nucleus / Q000502:physiology; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D017403:In Situ Hybridization; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016133:Polymerase Chain Reaction; D011784:Quail; D012333:RNA, Messenger / Q000235:genetics; D017384:Sequence Deletion; D014162:Transfection; D019014:fas Receptor / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D018076:DNA, Complementary; C097186:Faf1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D019014:fas Receptor