Sequences of apolipoprotein B 3' hypervariable repeat alleles

The apolipoprotein B-encoding gene (apoB) 3' end hypervariable repeats contain 11- to 16-bp A+T-rich sequences and are organized tandemly. Sixteen alleles varying in repeat number (26, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53, 55 and 58) were sequenced. Sequencing revealed a gradual extension of the number of bd (5'-TTTTATAATTAAAATA TTTATAATTAAATA) repeats [the fourth and fifth repeat units in variable-number tandem repeat 26 (VNTR26)] from alleles 26 to 58. In addition, four ef (5'-TTTTATAATTAAAATG TTTATAATTACATA) repeats (the eighth to fifteenth repeat units in VNTR26) in alleles 43, 45 and 47, and one ed (5'-TTTTATAATTAAAATG TTTATAATTAAATA) repeat (the sixth and seventh repeat units in VNTR26) in alleles 49, 51, 53 and 55 were deleted. Alleles 43, 45, 47 and alleles 49, 51, 53, 55, 58 also had variations at the 5' end of this repeat region (the first to third repeat units in VNTR26); the 3' end (the 16th to 26th repeat unit of VNTR26) of all alleles was invariant. This molecular event indicates a systemic expansion or contraction in this region.