GH3 CELL-SPECIFIC EXPRESSION OF KV1.5 GENE - REGULATION BY A SILENCERCONTAINING A DINUCLEOTIDE REPETITIVE ELEMENT

A silencer element (Kv1.5 repressor element; KRE) was characterized by deletion analyses in the promoter of Kv1.5, a voltage-gated potassium channel, The silencer element selectively decreases expression of Kv1 .5- and thymidine kinase-chloramphenicol acetyltransferase reporter ge ne constructs in cell lines that do not express Kv1.5 polypeptide. It contains a dinucleotide repetitive element (poly(GT)(19)(GA)(1)(CA)(15 )(GA)(16)), and self associates spontaneously in vitro to form complex es with slow electrophoretic mobility, Deletion of the repetitive elem ent abolished self-association in vitro and the silencing activity in transient transfection experiments in vivo, Electromobility gel shift assays of KRE with GH3 cells nuclear extracts detected the formation o f a unique DNA-protein complex, which was not detectable in Chinese ha mster ovary and COS-7 cells. This complex does not react with an antib ody against nonhistone high mobility group 1 protein, which binds KRE in gel retardation assays, These observations establish that a dinucle otide tandem repeat sequence, capable of self-association, forms part of a cell-specific silencer element in a mammalian gene.