Molecular cloning of a gene on chromosome 19q12 coding for a novel intracellular protein: analysis of expression in human and mouse tissues and in human tumor cells, particularly Reed-Sternberg cells in Hodgkin disease.
A novel protein, named NNX3, was molecularly characterized by cloning its cDNA, and its gene was mapped to chromosome 19q12. The equivalent mouse cDNA and gene were also cloned to allow us to analyze expression in murine in addition to human cells and tissues. Human and mouse NNX3 genes are composed of nine exons coding for proteins that are unrelated to any known protein. Signal peptides and hydrophobic domains are absent, corroborating their localization in the cytoplasm in transfected Cos cells. In Western blotting and immunoprecipitation, human NNX3 appeared as a doublet of Mr 64K-66K, while mouse NNX3 was a 70-kDa protein, both apparently much larger than the predicted 50 kDa, due in part to a stretch of 16-18 acidic residues hinging two nearly equally sized domains. In addition, phosphorylation of serine residues was demonstrated. Putative nuclear targeting signals were predicted, but NNX3 protein and two truncated versions remained localized in the cytoplasm of transfected Cos cells. NNX3 was expressed in embryonic and adult mouse tissues, particularly in brain, muscle, and lung. The expression of human NNX3 was most notable in human skeletal muscle and in ganglion cells and was also evident in human tumors and derived cell lines. This was confirmed by entries appearing in the GenBank EST database during the later phase of this study, representing partial NNX3 cDNA isolated from diverse neoplastic and developing tissues. Surprisingly, NNX3 was immunochemically detected in Reed-Sternberg cells of Hodgkin disease, in parallel with restin, a cytoplasmic protein we previously characterized (J. Delabie et al., 1993, Leuk. Lymphoma 12, 21-26). The cloning and comprehensive molecular analysis of NNX3 as presented will form the basis for elucidating its function and, conversely, will constitute a marker for Reed-Sternberg cells in Hodgkin disease.
Van Leuven
F
F
Experimental Genetics Group, Center for Human Genetics, Flemish Institute for Biotechnology, Department of Biochemistry, K.U. Leuven, Campus Gasthuisberg, Louvain, B-3000, Belgium. FREDVL@MED.KULEUVEN.AC.BE
Torrekens
S
S
Moechars
D
D
Hilliker
C
C
Buellens
M
M
Bollen
M
M
Delabie
J
J
D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D019556:COS Cells / Q000378:metabolism; D002352:Carrier Proteins; D002888:Chromosomes, Human, Pair 19; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D006689:Hodgkin Disease / Q000235:genetics*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D016539:Reed-Sternberg Cells / Q000502:physiology*; D012097:Repressor Proteins; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D011994:Recombinant Proteins; D012097:Repressor Proteins; C117184:URI1 protein, human; C485517:Uri1 protein, mouse