Identification of a silencing element in the chicken lipoprotein lipase gene I promoter: characterization of the silencer-binding protein and delineation of its target nucleotide sequence

Lipoprotein lipase (LPL) hydrolyzes triglycerides in chylomicrons and very low density lipoproteins (VLDL) and plays a central role in lipid metabolis m. It is regulated tissue-specifically. By deletion analysis, a negative re gulatory element was identified in the chicken LPL gene promoter at base pa irs (bp) -263 to -241. This sequence contained two palindromic halves with a three nucleotide spacer. Either half was sufficient for full inhibitory f unction. A protein complex bound specifically to this element and a high co rrelation was found between binding of the complex and inhibition of transc ription. Its molecular mass, evaluated by native gel electrophoresis and Fe rguson plot analysis, was 120 kDa, UV cross-linking followed by SDS-PAGE re vealed two protein subunits of 48 kDa and 44 kDa, respectively. This inhibi tory protein complex may contribute to the tissue-specific regulation of LP L gene transcription. It was much more abundant in liver than in adipose ti ssue and heart. Our data showed that this negative element inhibited transc ription even when placed at an upstream location (-666), but failed to func tion in the herpes simplex virus thymidine kinase promoter, indicating that it acted in conjunction with other element(s) in the chicken LPL gene to i nhibit transcription. (C) 1999 Elsevier Science B.V. All rights reserved.