Document 1076
 DOCN  M9471076
 TI    Regulation of transcription of the tax transgene and tax-induced genes
       in tumor cell lines of the LTR-tax transgenic mouse.
 DT    9409
 AU    Fontes JD; Univ. of California, Davis
 SO    Diss Abstr Int [B]; 53(9):4501 1993. Unique Identifier : AIDSLINE
       ICDB/94690786
 AB    The LTR-tax transgenic mouse develops peripheral neurofibromas as its
       primary pathologic feature. An in vitro cell line (Px-1 cells) derived
       from one of these tumors provides an excellent model for the study of
       tax-driven neoplasia. Using these cells, the role of tax in the
       trans-activation of cellular genes and the transgene itself was studied.
       It was determined that tax and activating transcription factor-1 (ATF-1)
       are both present in complexes that form between extracts of the Px-1
       cell line and viral long terminal repeat (LTR) DNA sequences. Treatment
       of Px-1 cells with protein kinase A and protein kinase C activating
       agents led to an intensification of these protein-DNA complexes. Using
       recombinant proteins, it was also demonstrated that tax increases the
       binding of ATF-1 to sequences in the LTR, a result that was also
       obtained by treating ATF-1 with protein kinase A in vitro. The
       expression of several growth factors was also examined in Px-1 cells.
       Potential tax-responsive DNA elements from promoter regions of several
       factors were examined for activity in Px-1 cells using reporter
       constructs. Only one sequence from granulocyte-macrophage colony
       stimulating factor (GMCSF) was found to increase expression over basal
       levels. Treatment of Px-1 cells with 8-bromoadenosine 3':5'-cyclic
       monophosphate (8Br-cAMP) led to an initial increase in messenger RNA for
       GMCSF, followed by a sharp decline. It was demonstrated that tax is
       phosphorylated in response to 8Br-cAMP treatment of the Px-1 cells, and
       that the previously identified tax-responsive GMCSF enchancer was
       responsive to 8Br-cAMP, even though there is no cAMP responsive
       enchancer present. (Full text available from University Microfilms
       International, Ann Arbor, MI, as Order No. AAD93-02595.)
 DE    Animal  Cyclic AMP-Dependent Protein Kinases/METABOLISM  Enzyme
       Activation  Gene Products, tax/*GENETICS  Granulocyte-Macrophage
       Colony-Stimulating Factor/GENETICS/  METABOLISM  Mice  Mice, Transgenic
       Protein Kinase C/METABOLISM  RNA, Messenger/METABOLISM  Repetitive
       Sequences, Nucleic Acid  *Transcription, Genetic  Tumor Cells, Cultured
       8-Bromo Cyclic Adenosine Monophosphate/PHARMACOLOGY  THESIS

       SOURCE: National Library of Medicine.  NOTICE: This material may be
       protected by Copyright Law (Title 17, U.S.Code).