title: Functional characterization of the X-linked inhibitor of apoptosis (XIAP) internal ribosome entry site element: role of La autoantigen in XIAP translation.
abstract: X-linked inhibitor of apoptosis protein (XIAP) is a key regulator of programmed cell death triggered by various apoptotic triggers. Translation of XIAP is controlled by a 162-nucleotide (nt) internal ribosome entry site (IRES) element located in the 5' untranslated region of XIAP mRNA. XIAP IRES mediates efficient translation of XIAP under physiological stress and enhances cell protection against serum deprivation and radiation-induced apoptosis. In the present report we describe the assembly of a sequence-specific RNA-protein complex consisting of at least four cytosolic proteins on the XIAP IRES element. We determine that the core binding sequence is approximately 28 nt long and is located 34 nt upstream of the initiation site. Moreover, we identify the La autoantigen as a protein that specifically binds XIAP IRES in vivo and in vitro. The biological relevance of this interaction is further demonstrated by the inhibition of XIAP IRES-mediated translation in the absence of functional La protein. The results suggest an important role for the La protein in the regulation of XIAP expression, possibly by facilitating ribosome recruitment to the XIAP IRES.
authors.affiliation: Apoptogen Inc.; Solange Gauthier Karsh Molecular Genetics Laboratory, Children's Hospital of Eastern Ontario, Ottawa, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Holcik
authors.forename: R G
authors.initials: RG
authors.lastname: Korneluk
mesh_terms: D001324:Autoantigens / Q000378:metabolism*; D001483:Base Sequence; D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D008969:Molecular Sequence Data; D038941:Polypyrimidine Tract-Binding Protein; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D012261:Ribonucleoproteins / Q000378:metabolism*; D012270:Ribosomes / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D051636:X-Linked Inhibitor of Apoptosis Protein; D000097585:SS-B Antigen
chemical_list: D001324:Autoantigens; D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D038941:Polypyrimidine Tract-Binding Protein; D011506:Proteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D014157:Transcription Factors; D051636:X-Linked Inhibitor of Apoptosis Protein; D000097585:SS-B Antigen; C496866:XIAP protein, human