Sp1- and octamer-consensus sequence binding proteins during lens fibre differentiation.
The pattern of factors binding to either the Sp1-consensus sequence or to the octamer sequence during in vitro rat lens fibre cell differentiation has been examined by electrophoretic mobility shift assays. With the Sp1-consensus sequence as probe, two major and four minor bands were seen. Three bands were present at all stages of differentiation, two are lost during terminal differentiation and one is present only in late differentiating cells. The octamer probe yielded three bands, which co-migrate with Oct2, Oct3 and Oct7. The exact identity of these factors has not been established. The Oct3-like band was detected only in epithelial cell extracts, the other two bands were also found in fibre cell extracts, whereby the intensity of the Oct2-like band decreased relative to that of the Oct7-like band during differentiation. In transfection studies, a rat gamma D-crystallin promoter in which the proximal activator has been replaced by a dimer of the Sp1-consensus sequence showed a gradual increase in activity with differentiation, in contrast, a similar construct with an octamer dimer was active only during late differentiation and mimicked the pattern of activation of the parental gamma D-crystallin promoter.
Brunekreef
G A
GA
Department of Molecular Biology, University of Nijmegen, The Netherlands.
van Genesen
S T
ST
Lubsen
N H
NH
D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D016384:Consensus Sequence / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D007908:Lens, Crystalline / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D016329:Sp1 Transcription Factor