homeostasis. Four human ACAT-1 mRNAs (7.0, 4.3, 3.6, and 2.8 kilobases (kb)) share the
same short 5′-untranslated region (exon 1) and coding sequence (exons 2–15). The 4.3-kb
mRNA contains an additional 5′-untranslated region (1289 nucleotides in length; exons X
a and X b) immediately upstream from the exon 1 sequence. One ACAT-1 genomic DNA
insert covers exons 1–16 and a promoter (the P1 promoter). A separate insert covers exon X …