CHARACTERIZATION OF THE CHICKEN APOLIPOPROTEIN-A-I GENE 5'-FLANKING REGION

Apolipoprotein A-I (apoA-I) is a major protein component of plasma hig h-density lipoprotein in all species studied, and plays an important r ole in cholesterol homeostasis. In an earlier study, we cloned and str ucturally characterized the chicken apoA-I gene. In this study, the 5' -flanking region of the chicken apoA-I gene was sequenced and function ally characterized. Sequence analysis of the 510-nucleotide 5' upstrea m region revealed the presence of TATA and CCAAT boxes. In addition, w e identified binding sites for several transcription factors such as S p1, AP1, and NF1.2. When the 5' fragment was ligated into a promoterle ss CAT vector and transfected into a chicken hepatocarcinoma cell line (LMH), the bacterial chloramphenicol acetyl transferase (CAT) gene wa s expressed, suggesting transcriptional regulation is associated with this region. Transfection studies with other 5' deletion constructs re vealed that the sequence spanning the region -82 to +87 contained the major transcriptional activity. DNase I footprinting, gel retardation, and Southwestern blot analyses showed that the fragment interacts wit h nuclear proteins.