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JF Codrington, HW Li, F Kutlar, LH Gu, M Ramachandran and TH Huisman
Department of Cell and Molecular Biology, Medical College of Georgia,
Augusta.
Hb A2 and its variant B2 (alpha 2 delta 2(16)(A13)Gly----Arg) were
quantitated in the blood of subjects with three different types of beta-
thalassemia and with the delta-B2 anomaly in cis or in trans to the
beta-thalassemia determinant. In one family, the delta-B2 mutation was in
cis to a newly discovered codon 47 (+A) frameshift. The levels of Hbs A2
and B2 were nearly the same and approximately 70% higher than those in
simple Hb B2 heterozygotes. In two additional families, the delta-B2
variant was in trans to either a deletional beta-thalassemia (1,393 bp)
involving part of the beta-globin gene and part of the beta- globin gene
promoter, or to the -88 C----T promoter mutation. In both instances, the Hb
B2 level was increased by approximately 80%, but the Hb A2 level was
increased by approximately 270% and 200%, respectively. These data indicate
two mechanisms that will cause an increase in delta chain production. One
is consistent with a general mechanism concerning the relative excess of
alpha chains in beta chain deficiencies which will combine with delta
chains to form variable levels of Hb A2 dependent on the severity of the
beta chain deficiency. The second concerns the loss of beta-globin gene
promoter activity, perhaps by an absence of (or decreased) binding of
specific protein(s) to this segment of DNA and a concomitant increase in
delta-globin gene promoter activity in cis.
This article has been cited by other articles:
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| Copyright © 1990 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
