Publisher Summary Transcriptional Control of the Human Apolipoprotein B Gene in Cell Culture and in This chapter discusses the recent progress in three major areas of work, with the apolipoprotein B (apo-B) gene— namely, mapping regulatory elements required for hepatic and intestinal expression of the human apo-B gene, using cell-culture models; ascertaining the functions of these regulatory elements in the expression of the apo-B gene in vivo, using transgenic mice; and using this knowledge to generate transgenic mice that overproduce human apo-B, to test its role in atherogenesis. Apo-B is the major and perhaps the sole protein component of low-density lipoproteins (LDLs) that play a central role in the metabolism and transport of cholesterol. Apo-B is the ligand responsible for the uptake and clearance of low-density lipoproteins from the circulation via the LDL receptor pathway (1-3). The delivery of LDL to its receptor and the ensuing catabolism regulate cellular cholesterol biosynthesis. Thus, apo-B and the LDL receptor are crucial to cholesterol homeostasis, and deficiencies in either protein may contribute to the development of atherosclerosis.