A novel glutamine-rich putative transcriptional adaptor protein (TIG-1), preferentially expressed in placental and bone-marrow tissues.
We used a subtractive hybridization protocol to identify novel expressed sequence tags (ESTs) corresponding to mRNAs whose expression was induced upon exposure of the human leukemia cell line K562 to the phorbol ester 12-O-tetradecanolyphorbol-13-acetate (TPA). The complete open reading frame of one of the novel ESTs, named TIG-1, was obtained by screening K562 cell and placental cDNA libraries. The deduced open reading frame of the TIG-1 cDNA encodes for a glutamine repeat-rich protein with a predicted molecular weight of 63kDa. The predicted open reading frame also contains a consensus bipartite nuclear localization signal, though no specific DNA-binding domain is found. The corresponding TIG-1 mRNA is ubiquitously expressed. Placental tissue expresses the TIG-1 mRNA 200 times more than the lowest expressing tissues such as kidney and lung. There is also preferential TIG-1 mRNA expression in cells of bone-marrow lineage.In-vitro transcription/translation of the TIG-1 cDNA yielded a polypeptide with an apparent molecular weight of 97kDa. Using polyclonal antibodies obtained from a rabbit immunized with the carboxy-terminal portion of bacterially expressed TIG-1 protein, a polypeptide with molecular weight of 97kDa was identified by Western blot analyses of protein lysates obtained from K562 cells. Cotransfection assays of K562 cells, using a GAL4-TIG-1 fusion gene and GAL4 operator-CAT, indicate that the TIG-1 protein may have transcriptional regulatory activity when tethered to DNA. We hypothesize that this novel glutamine-rich protein participates in a protein complex that regulates gene transcription. It has been demonstrated by Naar et al. (Naar, A.M., Beaurang, P.A., Zhou, S., Abraham, S., Solomon, W.B., Tjian, R., 1999, Composite co-activator ARC mediates chromatin-directed transcriptional activation. Nature 398, 828-830) that the amino acid sequences of peptide fragments obtained from a polypeptide found in a complex of proteins that alters chromatin structure (ARC) are identical to portions of the deduced open reading frame of TIG-1 mRNA.
Abraham
S
S
Department of Medicine, Division of Hematology/Oncology, Morse Institute of Molecular Biology, State University of New York, Health Science Center at Brooklyn, Brooklyn, NY 11203, USA.
Solomon
W B
WB
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D001854:Bone Marrow Cells / Q000378:metabolism*; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D020224:Expressed Sequence Tags; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D020014:K562 Cells; D056892:Mediator Complex; D008969:Molecular Sequence Data; D010920:Placenta / Q000378:metabolism*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D014018:Tissue Distribution; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
D018076:DNA, Complementary; C416944:MED15 protein, human; D056892:Mediator Complex; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D015500:Chloramphenicol O-Acetyltransferase; D013755:Tetradecanoylphorbol Acetate