Differentiation-dependent activation of the extracellular fatty acid binding protein (Ex-FABP) gene during chondrogenesis.
Chicken hypertrophic chondrocytes secrete the extracellular fatty acid binding protein (Ex-FABP), a lipocalin not expressed by their undifferentiated precursors. Genomic clones coding for the full protein are here structurally and functionally analyzed. We first determined that the promoter sequence markedly differs from that reported for the homologous p20K, and we confirmed by genomic DNA Southern analysis the exactness of our sequence. This is of relevance since we have identified another lipocalin gene within the region of discrepancy, indicating thereby the existence of a lipocalin cluster within the same chromosomal locus. By transient transfections with 5'-deletions and the chloramphenicol acetyl transferase (CAT) reporter gene, the region between nt -926 and nt -629 was shown to be strongly active, specifically in hypertrophic chondrocytes and not in dedifferentiated cells. Responsive elements for several potential transcription factors lay within this sequence. Among those, activating protein-1 (AP-1) was shown to be involved in the regulation of the Ex-FABP gene during chondrocyte differentiation, as indicated by electrophoretic mobility shift assay, AP-1 site mutagenesis and functional interference assays.
Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, Genoa, Italy. giannoni@cba.unige.it
Paolo
P
Giannoni
Adriana
A
Zambotti
Aldo
A
Pagano
Ranieri
R
Cancedda
Beatrice
B
Dozin
D000818:Animals; D030161:Avian Proteins; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D002645:Chickens; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D020219:Chondrogenesis / Q000502:physiology*; D050556:Fatty Acid-Binding Proteins; D017930:Genes, Reporter; D054834:Lipocalins; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D018808:Transcription Factor AP-1 / Q000378:metabolism
D030161:Avian Proteins; D002352:Carrier Proteins; C066299:Ch21 protein, chicken; D050556:Fatty Acid-Binding Proteins; D054834:Lipocalins; D018808:Transcription Factor AP-1