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The truncated Hoxa1 protein interacts with Hoxa1 and Pbx1 in stem cells
Author(s) -
Fernandez Cristina C.,
Gudas Lorraine J.
Publication year - 2008
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.22023
Subject(s) - homeobox , biology , microbiology and biotechnology , ectopic expression , immunoprecipitation , reporter gene , homeotic gene , gene , genetics , gene expression
Hox genes contain a homeobox encoding a 60‐amino acid DNA binding sequence. The Hoxa1 gene ( Hox1.6 , ERA1 ) encodes two alternatively spliced mRNAs that encode distinct proteins, one with the homeodomain (Hoxa1‐993), and another protein lacking this domain (Hoxa1‐399). The functions of Hoxa1‐399 are unknown. We detected Hoxa1‐993 and Hoxa1‐399 by immunoprecipitation using Hoxa1 antibodies. To assess whether Hoxa1‐399 functions in cellular differentiation, we analyzed Hoxb1 , a Hoxa1 target gene. Hoxa1‐993 and its cofactor, Pbx1, bind to the Hoxb1 SOct‐R3 promoter to transcriptionally activate a luciferase reporter. Results from F9 stem cells that stably express ectopic Hoxa1‐399 (the F9‐399 line) show that Hoxa1‐399 reduces this transcriptional activation. Gel shift assays demonstrate that Hoxa1‐399 reduces Hoxa1‐993/Pbx1 binding to the Hoxb1 SOct‐R3 region. GST pull‐down experiments suggest that Hoxa1‐399, Hoxa1‐993, and Pbx1 form a trimer. However, the F9‐399 line exhibits no differences in RA‐induced proliferation arrest or endogenous Hoxb1 , Pbx1 , Hoxa5 , Cyp26a1 , GATA4 , or Meis mRNA levels when compared to F9 wild‐type. J. Cell. Biochem. 106: 427–443, 2009. © 2008 Wiley‐Liss, Inc.