Galectin-4 is involved in p27-mediated activation of the myelin basic protein promoter.
Our previous studies have found that expression of p27 in oligodendrocytes enhances myelin basic protein (MBP) gene expression through a mechanism that involves the transcription factor Sp1. In this study we show that this activation only requires the N-terminal 45 amino acids of p27 containing a functional cyclin-binding motif. In an effort to identify other cofactors that are involved in the p27-mediated activation of MBP gene expression, a yeast two-hybrid assay was performed using an N-terminal truncated p27 and a mouse embryo cDNA library. Galectin-4 was found to interact with p27 in the yeast two-hybrid assay. This novel interaction was also confirmed using a glutathione-S-transferase interaction assay and immunoprecipitation assays. Expression of galectin-4 in primary oligodendrocytes was confirmed by western blot. Additionally, the MBP promoter could be activated by expression of galectin-4 in CG4 oligodendrocytes, similar to the effects of increased p27 levels. We also show that Sp1 and galectin-4 interact in cells, while a complex of all three proteins could not be found. We conclude that galectin-4 is involved in the p27-mediated activation of the MBP gene, possibly through modulation of the glycosylation status of the transcription factor Sp1.
Wei
Qiou
Q
Division of Basic Biomedical Sciences, Sanford School of Medicine of the University of South Dakota, Vermillion, South Dakota 57069, USA.
Eviatar-Ribak
Tamar
T
Miskimins
W Keith
WK
Miskimins
Robin
R
D000818:Animals; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000502:physiology*; D037541:Galectin 4 / Q000502:physiology*; D015870:Gene Expression; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D047468:Immunoprecipitation / Q000379:methods; D008156:Luciferases / Q000378:metabolism; D016296:Mutagenesis / Q000502:physiology; D004676:Myelin Basic Protein / Q000235:genetics / Q000378:metabolism*; D009836:Oligodendroglia / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000502:physiology*; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D014162:Transfection
D037541:Galectin 4; D004676:Myelin Basic Protein; D010446:Peptide Fragments; D050760:Cyclin-Dependent Kinase Inhibitor p27; D008156:Luciferases; D005982:Glutathione Transferase