title: MUC1-ARF-A Novel MUC1 Protein That Resides in the Nucleus and Is Expressed by Alternate Reading Frame Translation of MUC1 mRNA.
abstract: Translation of mRNA in alternate reading frames (ARF) is a naturally occurring process heretofore underappreciated as a generator of protein diversity. The MUC1 gene encodes MUC1-TM, a signal-transducing trans-membrane protein highly expressed in human malignancies. Here we show that an AUG codon downstream to the MUC1-TM initiation codon initiates an alternate reading frame thereby generating a novel protein, MUC1-ARF. MUC1-ARF, like its MUC1-TM 'parent' protein, contains a tandem repeat (VNTR) domain. However, the amino acid sequence of the MUC1-ARF tandem repeat as well as N- and C- sequences flanking it differ entirely from those of MUC1-TM. In vitro protein synthesis assays and extensive immunohistochemical as well as western blot analyses with MUC1-ARF specific monoclonal antibodies confirmed MUC1-ARF expression. Rather than being expressed at the cell membrane like MUC1-TM, immunostaining showed that MUC1-ARF protein localizes mainly in the nucleus: Immunohistochemical analyses of MUC1-expressing tissues demonstrated MUC1-ARF expression in the nuclei of secretory luminal epithelial cells. MUC1-ARF expression varies in different malignancies. While the malignant epithelial cells of pancreatic cancer show limited expression, in breast cancer tissue MUC1-ARF demonstrates strong nuclear expression. Proinflammatory cytokines upregulate expression of MUC1-ARF protein and co-immunoprecipitation analyses demonstrate association of MUC1-ARF with SH3 domain-containing proteins. Mass spectrometry performed on proteins coprecipitating with MUC1-ARF demonstrated Glucose-6-phosphate 1-dehydrogenase (G6PD) and Dynamin 2 (DNM2). These studies not only reveal that the MUC1 gene generates a previously unidentified MUC1-ARF protein, they also show that just like its 'parent' MUC1-TM protein, MUC1-ARF is apparently linked to signaling and malignancy, yet a definitive link to these processes and the roles it plays awaits a precise identification of its molecular functions. Comprising at least 524 amino acids, MUC1-ARF is, furthermore, the longest ARF protein heretofore described.
authors: Department of Cell Research and Immunology, Tel Aviv University, Ramat Aviv, Israel.
authors: Michael
authors: M
authors: Chalick
authors: Department of Cell Research and Immunology, Tel Aviv University, Ramat Aviv, Israel.
authors: Oded
authors: O
authors: Jacobi
authors: Department of Cell Research and Immunology, Tel Aviv University, Ramat Aviv, Israel.
authors: Edward
authors: E
authors: Pichinuk
authors: Department of Biopathology, Institut Jean-Godinot, Reims Cedex, France.
authors: Christian
authors: C
authors: Garbar
authors: INSERM U976, Hôpital Saint Louis, Paris, France.
authors: Armand
authors: A
authors: Bensussan
authors: The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors: Alan
authors: A
authors: Meeker
authors: Department of Cell Research and Immunology, Tel Aviv University, Ramat Aviv, Israel.
authors: Ravit
authors: R
authors: Ziv
authors: Department of Pathology, Meir Medical Center, Kfar Saba, Israel.
authors: Tania
authors: T
authors: Zehavi
authors: Department of Cell Research and Immunology, Tel Aviv University, Ramat Aviv, Israel.
authors: Nechama I
authors: NI
authors: Smorodinsky
authors: Division of Molecular Genetics, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
authors: John
authors: J
authors: Hilkens
authors: Institute of Biochemistry II, Medical Faculty, University of Cologne, Köln, Germany.
authors: Franz-Georg
authors: FG
authors: Hanisch
authors: BioModifying LLC, Silver Spring, Maryland, United States of America.
authors: Daniel B
authors: DB
authors: Rubinstein
authors: Department of Cell Research and Immunology, Tel Aviv University, Ramat Aviv, Israel.
authors: Daniel H
authors: DH
authors: Wreschner
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D003062:Codon; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D051379:Mice; D018396:Mucin-1 / Q000235:genetics* / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*
chemical_list: D003062:Codon; D018396:Mucin-1; D012333:RNA, Messenger