Single-stranded DNA-binding proteins regulate the abundance and function of the LIM-homeodomain transcription factor LHX2 in pituitary cells.
A family of single-stranded DNA-binding proteins (or SSBPs) has been shown to augment the function of LIM-homeodomain (LIM-HD) transcription factors in embryogenesis by interaction with LIM domain-binding protein-1 (LDB1). No DNA-binding complex has been described, however, containing a LIM-HD protein, LDB1, and SSBP, and the mechanism by which SSBPs affect LIM-HD function had not been elucidated. Through use of electrophoretic mobility shift, antibody supershift, and ChIP analyses, we show that an Lhx2-Ldb1-Ssbp3 complex binds a specific element in the Lhx2 target gene Cga (encoding the alpha subunit of glycoprotein hormones) in the alphaT3-1 pituitary cell line. Using overexpression and knockdown approaches, we demonstrate that SSBP3 inhibits Lhx2 and Ldb1 turnover, stimulates assembly of this DNA-binding complex, promotes its recruitment to the Cga promoter, and enhances Cga transcription. These studies provide novel insights into the regulation of pituitary gene expression and LIM-HD function more generally.
Department of Medicine, Vanderbilt University, Nashville, TN 37232, USA.
Ying
Y
Cai
Zhixiong
Z
Xu
Lalitha
L
Nagarajan
Stephen J
SJ
Brandt
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D004277:DNA, Single-Stranded / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D005786:Gene Expression Regulation; D015292:Glycoprotein Hormones, alpha Subunit / Q000235:genetics; D018398:Homeodomain Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D060588:LIM Domain Proteins; D060850:LIM-Homeodomain Proteins; D051379:Mice; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D015292:Glycoprotein Hormones, alpha Subunit; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; D060850:LIM-Homeodomain Proteins; C102084:Ldb1 protein, mouse; C489784:Lhx2 protein, mouse; C504093:Ssbp3 protein, mouse; D014157:Transcription Factors